Answers to discussion topic questions in Unit 1

Please make sure you understand the answers before you attempt the practice quiz or unit test

Scientific Method

Is technology a trap?

We have built a society that relies on technology, not just for conveyance, but for survival.  Think of what would happen if we lost electric power for an extended length of time.  In one week, the food in the pantry gets low, you have no water or gasoline.   No stores, banks, internet, etc.   In one month, total chaos!  Simply put, we can't support a huge urban population without technology.  Things would get real bad, real fast.  Can you grow your own food?  How do you prevent others from raiding your stuff?  Could this happen?  Just Google something called the Carrington Event.  An 1859 solar storm dismantled our only form of mass communication ... the telegraph system.  If a similar event happened today the cost could be in the trillions of dollars and possibly weeks (or a year?) without electric power (worst case scenario).  The trap is sprung.  Have a nice day!!!

Look up "deductive reasoning" and "inductive reasoning".  Define both and give an example of each.  Which one best describes the scientific method?

In deductive reasoning you make a conclusion based on known truths.  The result is guaranteed to be a truth provided the initial statements are true.  Example: All mammals are warm blooded.  Humans are mammals.  Therefore, humans are warm blooded.  In deduction, you work from the general to the specific.  In inductive reasoning, you base your conclusion on observations.  That is, you work from the specific and work toward the general.  Example:  I am warm blooded.  Every mammal I've ever observed is warm blooded.  Therefore, I must be a mammal.

Science builds its "truths" based on testable observations.  The theories in science were not handed to us, but rather built up from many observations.  Science is an inductive process.  Inductive reasoning (like science) is subject to error.  One observation can topple the status quo.

Is "intelligent design" a scientific fact, law, hypothesis, or theory?  Does it belong in a science class?  Support your answer.

I would call ID an un-testable hypothesis.

My Opinion:  Intelligent design is a belief based on faith ... not observation.  Science can only deal with testable observations and also adheres to the notion that the universe behaves in "natural processes".  Intelligent design is a way of understanding how we came to be, but it is NOT science.  That is not to say that your faith beliefs (whatever they may be) are worthless.  I have strong religious beliefs, but you are not going to hear them from me because this is a science class.

I've heard the argument that biologists cannot answer questions like "how did life begin?".  Therefore, ID offers an alternative explanation and should be taught in the classroom.  There are MANY unanswered questions in science.  But science doesn't simply plug the holes with an un-testable explanation.  If that were the case, you could simply make anything up that can't be tested and offer it as an "alternative" solution.  Science doesn't work that way.  Remember, that science is a process, not an answer.

Theory, Law, Hypothesis, Fact:

I'll pick on one discipline (Geology) to give an example:

Theory: Plate Tectonics: The crust of the earth is fragmented into rigid slabs that move with respect to each other. Their motion explains the current topology of the earth's crust as well as events such as mountain building, volcanoes, and earthquakes.  Note: A theory is a grand statement which may encompass many observable phenomena.
Law: In a layer of undisturbed sediments, the oldest layer is found on the bottom and the youngest layer on the top.  A law usually shows how two or more variables are related.  In this case, position is related to age.  Note: Many laws are written in the form of an equation.  If you see an equation, think law!
Hypothesis: It is possible to predict an earthquake by noticing the behavior of animals just prior to the event.  Note: There is no current reliable way of predicting an earthquake but this is one possible connection that is currently being investigated.  It may be difficult to distinguish between a law and hypothesis.  If it looks like a guess, think hypothesis.
Fact: The tsunami of 2004 was a magnitude 9+ on the Richter scale.  This is a recorded, undeniable statement which all geologists can agree.

What is "junk science"?  In your answer please make sure you make it clear how it differs from science.  Give 3 examples why anyone would be motivated to use junk science.

Junk science are studies which have not been tested, scrutinized by peer reviews, not reproducible, and/or based on biased or misleading data.  Junk science studies are often used when the conclusions of the study are relied on to make a decision or settle an argument ... be it legal, political, profitability, or ego.  One who wants to sway opinion and/or support their agenda may even be using junk science without even knowing it.  Sometimes junk science is easy to spot.  For example, if the tobacco industry funds a plan to study the health issues related to smoking .... well, guess what their conclusions will be?  Other times it is not so easy to spot.  This is where YOU come in.  Your job is to be an informed citizen and base your decisions on solid studies ... not what you read in a blog, seen in an ad, or heard on a talk show.  Go to the actual studies and learn for yourself what are facts and "alternate facts". 

Natural Laws

1. When you slide a book across a tabletop, what does it do (after it leaves your hand)?  What kind of motion is this?  How do you explain this behavior in terms of Newton's laws of motion?
   
   The book comes to rest (deceleration or negative acceleration).  The friction force between the table and book provides the required force to overcome the inertia of the book.  This is an application of Newton's Second Law of Motion
    
2. If you drop a coin from your hand, what kind of motion do you observe? Which one of Newton's laws of motion apply?
   
   It accelerates so the Second Law applies again.  The force comes from the weight of the coin.
    
3. If you drop a feather and a coin at the same time, why does the coin hit the ground first?  What would you expect in a vacuum?
   
   The coin hits the ground first.  Air friction plays a big role here.  In a vacuum, they both accelerate at the same rate and land together, but in air the net force on the object is a combination of the weight (acting downward) and air friction (acting upward).  If those two forces are equal and opposite, the feather will fall with a constant velocity (Newton's First Law applies) because as far as the feather is concerned, balanced forces are the same as no force acting on the feather.
    
4. A skydiver eventually reaches a terminal velocity of 120-150 miles per hour (i.e. a constant velocity).  Why?  Explain in terms of Newton's laws.
   
   See the last answer.  The skydiver accelerates initially but as air friction builds, the rate of acceleration drops to zero when air friction (upward force) equals the weight of the skydiver (downward force).  Then Newton's First law kicks in and the person falls with a constant velocity.
    
5. Explain why a car moving on a circular track with cruise control "on" is actually accelerating.  Hint: Think how the accelerometer would behave if resting on the dashboard.
   
   The best way to show acceleration here is to show that there is a force acting on you as you drive in circles (and then think Newton's second law).  Ask any NASCAR driver about going around corners.  They feel the sensation of being "dragged" to the passenger side (often erroneously called centrifugal force) ... but that is actually just their inertia compelling them to move in a straight line.  To prevent that, friction with their seat (as well as seat belts) provide a very real force to keep the driver in their seat.  This force is always acting toward the center of the circle (centripetal force) and Newton says that whenever a force acts on you, you have accelerate.  Even though you are not speeding up or slowing down .. you ARE accelerating because you are changing direction.  An interesting analogy is seen when a satellite is orbiting the earth.  Consider this: If you throw anything horizontally, you know it will accelerate toward the earth as it arcs toward the ground.  Now throw it very fast (horizontally) and at a very high altitude  (so there is no air friction).  It does the same thing ... it falls with an arc toward the earth.  The difference here is that it is falling toward the earth (acceleration) but the curvature of the earth comes into play.  If the arc of this "falling" satellite is exactly the same as the curvature of the earth, it never hits the ground!  It will continue to accelerate toward the earth but never get closer to the earth at the same time.  Freaky!
    
6. What is the advantage of having a more massive camera when taking a picture?
   
   The more massive the camera, the more inertia it has.  That means it has a higher tendency to remain at rest.  Isn't that what you want a camera to do?  - NOT move around too much when taking a picture?  Here is a thought.  Think of MASS as a measure of inertia ... not weight.  That is, if you were in deep space, you might not have any weight (because you aren't gravitationally attracted to anything) but you would still have inertia.  It would still require a force to make you change your state of motion.  The more massive you were, the larger the required force to produce the same effect.  This is exactly how they "weigh" astronauts.  In space, a scale is useless so they strap the astronauts to a chair that "jiggles" them.  If they have been eating too much, it takes a bigger force to jiggle them.  Try this with some different weights.  Move the weight rapidly back and forth and notice the difference in the required force as you change weights.  You are not "weighting" the weights - you are "massing" them.  Think of mass as the tendency to resist changes in motion.
    
7. Design a device that will turn on a warning light when the acceleration reaches some critical value.
   
   Look at the animation of the accelerometer (a mass suspended by springs).  Now imagine an electrical contact that is made when the mass is displaced from the central position at your critical value.  Note: Later in this class you will see that there are many ways to detect slight displacements of the mass ... all of which can be programmed by a microcontroller to alert you when the mass (in your accelerometer) has been dislodged from its rest position.
    
8. Give an example where such a device (mentioned in the last question) might be useful.
   
   You would want to warn any jet pilot when he/she is close to fainting.  However, a more common application of an accelerometer is found in the hand held remote of the Wii gaming system (along with a sophisticated LED position sensor).  The same technology is built in to most smart phones.  I was amazed the first time I saw the Google Sky Map app on my phone.  Point the phone around the sky and motion sensors translate the movement of the phone to a star map display.  Amazing (plus the app is free)!
    
9. A magician will snap a silk tablecloth away and the plates, glasses, and silverware remain in place.  Explain this trick.
   
   There are two parts to this trick.  One part of this trick deals with minimizing any forces on the tableware.  In this case, friction.  Silk offers very little friction and if yanked very quickly, that force acts for a short time so there really isn't a large force and it doesn't act on the tableware for very long which equates to very little acceleration.  In theory, it has to move but only just a little.  The second part of the trick is to use massive tableware.  Remember that the larger the mass, the more inertia an object has.... i.e.. the tendency to resist changes in motion.
    
10. Design an earthquake detector using the concept of inertia and ordinary household items.
    
    The ancient Chinese made a device that not only recorded the earthquake, but also the direction of the wave.  Chang Heng's seismoscope was one of the first.
    
    
    As the wave passed, the disturbance was enough to dislodge a small ball from a dragon which would drop into a toad's mouth.  There were 8 dragons around the circumference of the vase so the direction of the epicenter was determined based on which balls dropped.  Today, a heavy bob remains stationary as the shaking earth wiggles below it.
    
    
     
11. Newton also wrote a "third law" regarding forces (motion).  What was this law?  Hint: It was not "what goes up" or his law of Gravity (which was a pretty good one)!   Give 3 examples of this "third law".
    
    For every action (force) there is an equal and opposite reaction (force).  This simply means forces always act in pairs.  If object A exerts a force on object B, object B exerts and equal and opposite force on object A.  In the analysis of the motion of an object, you are only concerned with the forces acting ON the object ... not BY the object.  One example occurs when stepping off a boat to the pier.  When you jump off, you exert a force on the boat (which makes it move out into the lake).  The reaction is the boat pushing you to the pier.
     
12. When two surfaces are in contact and moving with respect to each other, what are the two most important factors which determine the amount of friction force you encounter?
    
    In physics 101 you are given the basic formula F_k = μ_k N  where F_k  is the kinetic friction force ,  μ_k is the coefficient of kinetic friction, and N is the "normal force".  Basically the coefficient of friction deals with the type and condition of the surfaces ... metal, wood, concrete, ...smooth or rough. There are volumes of tables for just about any material you can think of.  μ_k is a unit-less number.  The other variable, N, refers to the force pressing the surfaces together.  For example, the reason your car brakes work is because you apply a large "normal" force between the brake pad and drum (or rotor).  You can also notice this if you rub your hands together.  The more perpendicular force you apply (while rubbing), the warmer your hands get.  Note: speed and surface area are generally NOT big factors (which are common guesses).

Engineers go to great lengths to find clever ways to reduce friction.  Give at least one very specific example.  Look over all the posts from other students to avoid any repetitions.

Most people know that we use lubricants to reduce friction.  This is to prevent solid surfaces from making physical contact.  Scientists have used boric acid in motor oil to radically reduce wear in engine parts.  The molecules form in sheets that slide across adjacent sheets like cards in a deck.    There are many other good answers here - low friction bearings (Teflon), aerodynamic car design (to reduce air friction), magnetic levitation in trains to eliminate physical contact with a surface (similar to air hockey) ... even Michael Phelps swimsuit was designed to reduce friction (go USA).

Living in a frictionless world

Typical answers are:  we can't walk, cars can't move, we can't pick things up in our hands.   This is all related to Newton's first law that states an object at rest will stay at rest unless a force is applied.  In these cases, the force relies on friction.   Some students point out that things in motion will continue in motion (again, Newton's 1st law) ....  cars can't stop or turn, etc.  Basically, things would be a mess without friction.  On rare occasions I get students who goes beyond these answers ....  like  "if my car was at rest on a hillside and friction disappeared, the car would accelerate down the hill (there is still gravity and the brakes don't work and let's hope the road is straight) and then decelerate going up the next hill until it came to rest.  It would then start accelerating backwards downhill until it got back to the original starting point (no losses to air friction or other places).  This would continue forever."

Tough Challenge Question

All physics students know that things in a vacuum fall with an acceleration of "g".  Easy Part:  What is "g"?

The acceleration of gravity at the earth's surface  (in a vacuum) is 9.8 m/s² or 32 ft/s².  This means that every second the speed increases 9.8 m/s or 32 ft/s.

Hard Part:  Why do all objects in a vacuum accelerate at this rate?  Explain in terms of Newton's laws of motion.  In your answer, resolve this conflict:

If I drop a 10 pound weight and a 20 pound weight from rest, the 20 pound weight should accelerate twice as fast since it is pulled (by gravity) with twice the force.

The 20 pound weight is pulled with twice the force as the 10 pound weight so you may think that it should accelerate at twice the rate.  However, the 20 pound weight also has twice the mass (double the inertia) so it has a higher resistance to change its state of motion.  Mass and weight are actually two different physical quantities but they are related.  Weigh is the gravitational pull on an object - a force.  Mass is a measure of inertia - how sluggish it is to changes in motion.  If an object has twice the mass, it also has twice the weight.  The exact conversion factor is w = mg.  Basically, these two factors (mass and weight) cancel each other out and everything accelerates with the same value (in a vacuum).   Here is the math:

Go back to Newton's second law a = f/m.  For any falling object (in a vacuum):  f=w (weight)  substituting we get

a = w/m  but since w=mg we can substitute again to get a = mg/m  which reduces to a=g

Energy

1. If you are stationary and holding a bag of heavy groceries, are you doing work?  Are you expending energy?
   
   By definition, you are doing no work because nothing is moving.  However, you are expending energy because our bodies are not rigid solids.  A chair can hold a weight without refueling, however your body needs to exert muscles to hold an object at rest.  
   
    

2. What if you are walking forward?  Does your answer change?
   
   By definition, the upward force you exert on the bag to hold it up is doing no work because the motion is not in that direction.  I will certainly give you credit if you explain your NO answer this way.  In fact, that is what I was looking for in your answer.  But actually the answer is YES - you are actually doing a very little amount of work because you are exerting a (much smaller) forward force on the groceries and they move (in that direction).    You can make this a very difficult question if you like.  One could argue that you are only doing work if the bag of groceries is accelerating (in a vacuum) in the forward direction and not doing work if you are moving forward (in a vacuum) with a constant speed.  However,  if you were initially at rest, you need to do some work to get the bag moving in the forward direction (in real air).  Add in any air friction (but not a lot since you are mot moving very fast) and I guarantee you are doing some work.
    

3. Robert Hooke discovered a law related to springs.  In simple terms, what was this law telling us? (no equations please)
   
   The bigger the applied force on a spring, the more it stretches (where stretch is the distortion from the rest position).  OK .. I will give the equation F = kx  where k is a constant and x is the stretch.
    

4. Why do you feel cool when you initially get out of a pool (especially on a windy day)?
   
   This has everything to do with latent heat. When you get out of the water, water rapidly evaporates from your body.  Any phase change is associated with a HUGE change in energy.  Heat is extracted from your body and is used to vaporize the water.  You cool down.  Our bodies sweat to cool us down.  This is also why you feel so uncomfortable when the heat and humidity are high.  The high humidity means the rate of evaporation is lower so you don't have an efficient way to cool off your body.
    

5. Why are steam burns so painful?
   
   Latent heat!  Look at the numbers in question #14.  When water changes from vapor to liquid, it must release LOTS of heat.
    

6. Think of a way you can determine the energy content of an apple (how many calories it contains).  Hint: besides looking it up.
   
   Scientists use a device call a "calorimeter" or "bomb calorimeter" to do this.  Here is how this works.  You find a way to burn the apple to release the heat (I'm guessing you would dehydrate the apple first).  The heat produced is the same amount energy you would get if you digested the food.  The combustion process is done so that all the heat is used to warm water (the entire process is done in a chamber surrounded by water).  The heat gained by the water equals the heat released by the apple.  You need to make appropriate adjustments ... like taking into account any heat you added to burn the food and other minor stuff, but the end result is you get the chemical energy stored in the apple.  Your answer may vary.
    

7. Lift up any object and trace the energy it takes as far back as you can.
   
   The energy comes from the food you eat (and the oxygen you breathe .. which is a necessary part of digestion).  If you are a vegetarian, the energy in your food comes from photosynthesis.  If you eat meat, it comes from the biomass of animals but that is built up from plants using photosynthesis.  The sunlight that drives photosynthesis comes from nuclear fusion reactions inside the sun.  Want to go another step back?  The atoms that fuse within the sun were byproducts of the big bang (the thing that started the universe).  At first, all energy was radiation, but as the universe cooled, some of that energy was converted to matter .... using Einstein's E=mc^2 equation.  If you can go back further than this .... you should be a physics major.
    

8. Now consider the many possible ways this same energy get transformed once you drop this object.
   
   The answers will vary.  Initially you are converting gravitational potential energy to kinetic energy.  Then it hits something and just about anything can happen.  It could be used to change the shape of the surface it hits (and even the shape of the object).  It can make sound energy.  It can produce heat.
    

9. Now consider your scenarios (from the last question) in the reverse direction (like running a film backwards).  Do any of these energy transformations violate the first law of thermodynamics?  Which transformations seem to violate the second law of thermodynamics?
   
   None of these transformations violate the 1st law of thermodynamics but most will violate the 2nd law of thermodynamics.  Have you ever watched a movie run backwards?  The reason it looks funny is because you witness energy conversions in ways you don't normally see.   Have you ever witnessed a ball (at rest) just start bouncing  .. higher and higher .. until it pops up to your hand (at the same time the surroundings are getting cooler)?  I doubt it! 
    

10. Why is entropy sometimes referred to as the "arrow of time"?  This question is the hardest.  In your answer give a specific example how the second law of thermodynamics can be used to measure the direction of time.
    
    The last question should shed some light on this answer.  It is not just energy conversions but the general behavior of matter that seems to take a "one way" trip through time.  In the backwards movie, you see smoke particles slowly concentrate toward a candle (and then the candle lights up).  Cards lying randomly on the floor jump together to a single deck in someone's hands.  Entropy is all about "order" going toward "disorder".  If you had many individual pictures of these events, it would be possible to place them in the correct chronological order based on your understanding of entropy.
     

11. What seems to be the ultimate fate of the universe (from an energy perspective)?  That is, what form of energy (mentioned in the eBook) is the only one left in the very, very distant future?
    
    Most forms of energy convert to heat (random motion of molecules).  The ultimate state of "disorder" is to have the entire universe all at one temperature.  Physicists call this the "heat death" of the universe.  Astronomers have known for some time that the universe is expanding.  Recently, they have found that the rate of expansion is accelerating with time (totally unexpected).  It looks like we are headed towards this "heat death" (but don't worry, we still have plenty of time yet).  If this expansion continues, at some very distant point in time, all forms of matter will be stripped down to a subatomic level and all at the same temperature.  Kind of a boring end to the universe if you ask me.
     

12. Astronomers have discovered a new form of energy known as "dark energy".  How much do we know about it?  What effect is it having?
    
    Edwin Hubble discovered that the universe is expanding in the 1920’s.  Almost all galaxies are moving away from each other …. a result of the Big Bang.  However, to the surprise of astronomers, they also discovered (in the 1990’s) that the rate of galactic recession is increasing with time.  This was totally unexpected!  As a result, they “invented” a new form of energy to explain it – Dark Energy.  Astronomers have no idea about the nature of this form of energy other than it produces this anti-gravity like effect.  If this stuff really exists, there is A LOT of it.  After all, moving the universe around isn’t easy.
     

13. List 5 units of energy and find the definition of each unit.
    
    Answers will vary.  Some are BTU, Joule, kilowatt-hour, erg, electron volt.  I left out the definitions which are easy to look up.
     

14. How much energy does it take to raise 1 gram of water 1 degree Celsius?  Hint: Look up the specific heat of water.  How much energy does it take to convert 1 gram of water into a vapor?  Hint: Look up the latent heat of vaporization for water.  Which takes more energy - heat 1 gram of liquid water from its freezing point to its boiling point OR vaporize 1 gram of water at 100C?
    
    By definition a calorie is the amount of energy needed to raise 1 gram of water 1 degree Celsius.  To convert 1 gram of water from its freezing point (0 C) to its boiling point (100 C) takes 100 calories.  It takes 80 calories to melt one gram of ice to water and 540 calories (wow!) of heat to vaporize 1 gram of water.  It should be clear why steam burns are so painful.  540 calories per gram is a LOT of heat that must be released when water condenses from a vapor.  It also explains why a hurricane has so much energy since so much water vapor is condensing in a concentrated area.
     

15. The average human's metabolism produces about 400 BTU of heat per hour if awake but stationary, 250 BTU/hr (when sleeping).  How many bananas would you need to eat each day to break even?  Hint: Assume each banana contains 80 calories.
    
    Assume you sleep 8 hours a day.  250 x 8 = 2000 BTU (sleeping)     400 x 16 = 6,400 BTU (awake)   8,400 BTU = 2,116 calories (nutritional) or about 26 bananas.  Note: a nutritional calorie is NOT the same as the calorie defined in the last unit.  This is a source of confusion for many people.  PS: I would not eat 26 bananas in a day!
     

16. What horsepower motor is needed to lift 50 bales of hay (at 100 pounds each) to a height of 10 feet if the task must be completed in 10 minutes?  Assume no friction or power losses.
    
    50 x 100 = 5,000 pound x 10 feet = 50,000 ft pounds of work.   If you like, you can keep time in minutes but I'll convert to 600 seconds.  Power required = 50,000 / 600 = 83.3 ft pound/s.  Convert this to horsepower.  Note: You would use foot pound - force/second.  Answer = .15 hp
     

17. A 3 hp pump is used to lift water to the top of a 30 foot building.  How many gallons can it move every minute?
    
    3 hp = 99,046 foot - pound (force) / minute  (using this link)
    
    Power = energy / time
    
    99,046 = 30 x W / 1    where W = weight in pounds
    
    W = 3302 pounds of water         = 396 gallons of water (from this link under miscellaneous)
    
     

18. Does your utility company's monthly bill charge you for energy or power?  Explain.  Consider appliances (TVs, computers, etc).  How are they rated - power or energy?  Explain.
    
    The utility gives you a monthly bill for the amount of energy you use.  I guess you could argue that time is involved in this last statement, but check your bill, it is listed in energy units .. not power units.  Your appliances are rated by power.  The longer you run the appliance, the more energy it consumes.
    
    Note: Many appliances are rated by how much current it draws in amps.  If your device is listed in amps, multiply by 120 volts to get the power rating in watts      P = VI
     

19. What are the standard units used (by the company) for electricity?  For natural gas (or whatever you use for heat)?  Provide a number for each unit from your last bill (cost per unit, total units used, as well as total cost).  Convert the total units used for each (electric vs. heat) to Joules for the sake of comparison.  Which is the largest and costliest? Make a pie chart to show where your household uses the most energy (one by Joules and another by cost)
    
    Electricity is rated in kilowatt - hours
    Natural gas is rated in therms
    
    I'll use data from my home as an example:
    
    
     

    	Summer Bill - August	Winter Bill - December
    Electric	28 kwh / day = 100 800 000 joule	29 kwh / day = 104 400 000 joule
    Natural Gas	.61 therms / day = 64 343 044 joule	4.25 therms / day = 448 291 700 joule
    Electric	$3.21 / day	$3.24 / day
    Natural gas	$.79 . day	$4.78 / day

    
                                               
    
    
    

    As you might guess, I use a higher percentage of natural gas in winter (mainly for heating).

     

20. What does an air conditioners SEER rating refer to?  Are you comparing energy, power or both?  Is a higher number good or bad?
    
    Air conditioners use electrical energy to MOVE heat.  The heat is moved from the air inside of your room to the outside air.  The same can be said about your refrigerator.  So the efficiency of any "heat mover" can be made by comparing the amount of actual heat energy moved to the amount of electrical energy it takes to move the heat (electricity used) during the same period of time.   It is a ratio, ... BTU cooling divided by electric energy used (in watt-hours).  You are comparing energy units here - BTU/watt-hours.  The higher the number, the more efficient the unit.  In unit 5 we see how refrigerators and air conditioners work.
     

21. A car typically needs 10-20 horsepower to move at constant speed on a level surface.  Where do you think most of the energy is dissipated under these conditions?
    
    A car running on a flat highway at a constant speed only needs 10-20 hp to overcome friction (air friction mostly, but also rolling and mechanical friction).  However, your car needs much higher power for accelerating (overcome inertia) and climbing hills (gains in gravitational potential energy).  Hybrid cars have a very small gasoline engine to handle the common highway driving but uses the power assist of an electric motor to accelerate and climb hills.  For example, the Toyota Prius has a gasoline engine rated at about 60 HP which can easily handle highway driving on a flat surface.  These cars are cool!
     

22. Why do you think most cars have a power rating from 100-200 horsepower (considering the facts given in the last question)?  List at least two reasons why all this extra power is needed.
    
    see above
     

Levers

1. The mechanical advantage of a machine is often referred to as "actual" or "ideal".  What is the difference between these two terms?
   
   The ideal case assumes a frictionless world.  In this situation you can calculate the ideal MA by the ratio of lever arms.  However, in the real world there are energy losses due to friction.  The actual MA is found from the ratio of forces (load/effort).  In the real world, friction in levers is relatively low so IMA and AMA are almost equal.  This is NOT the case with wedges, which encounter a lot of friction.
    
2. Under what conditions will a first class lever provide a mechanical disadvantage?  Where is this commonly seen?
   
   If the effort lever arm is shorter than the load lever arm, there is a mechanical disadvantage.  This is commonly seen in heavy machinery that use hydraulics as the effort force.
    
3. In all our examples, we have ignored the actual weight of the lever itself.  Does this come into play at all in reality?  If so, explain how in a practical or mathematical way.
   
   All levers have weight.  From a mathematical point, you can treat the weight of the lever as if it were a single force applied at the geometric center of the lever.  In this case, it is capable of producing torque about the fulcrum.  A draw bridge is a giant lever where the "load" is the bridge itself.  Can you think of a situation where the torque produced by the weight of the lever alone is enough to lift some load?  As a kid we played on teeter-totters where it was possible to shift the fulcrum point (off center) so it was possible for one kid to play solo ...  no one wanted to play with me  :(
    
4. What is happening when you put your car's automatic transmission into a lower gear (sometimes labeled 1 or L1)?   Under what conditions would this be appropriate?
   
   The lower gear does NOT give your car more power.  This transmission setting allows you to allocate the power so you are trading RPM's for torque.  This is great for pulling cars out of ditches.  You need lots of torque at the wheels .. not speed.  Note: It is a good idea to use a slightly lower gear when pulling a trailer.  Trucks often shift to a lower gear when going down steep slopes in a technique called "engine braking".  The idea is to feed energy INTO the engine ... saving the brakes.  In this case, the energy is dissipated through the engine in the compression stroke and into the flywheel.
    
5. Give 3 examples where a force is applied some distance from a pivot point and no torque is produced.
   
   On a bike, there are pedal positions where the force produces no torque (when the pedal is at the very top or bottom).  The same can be said about a piston when it is in the "top-dead-center" position.  Electric motors also have a "dead" position.  In all these cases, imagine trying to push on a lever but the force is directed through the pivot point.  Use the image below to imagine the train wheel is rotated 90 degrees (in either direction).  You should see that no matter how hard the engine pushes, there is NO torque delivered to the wheel.
    
6. One of these locomotive wheels was designed to transport freight and the other is designed to transport passengers.  Can you guess which?  Explain.
   
   The locomotive with the smaller drive wheel is designed for freight and the larger wheel for passengers. Both wheels are (as depicted) 3rd class levers and as such, have a mechanical disadvantage for the sake of greater motion.  Since the input forces (and application locations) are the same in both cases, we can assume that both wheels receive the same input torque ... so the output torque of each wheel is also the same.   Think of the radius of each wheel as the output lever arm.  The smaller wheel allows more force to be applied to the ground to move the heavier freight.   So the greater the radius of the wheel, the lower the output force to the ground.
   
   The larger wheel may be at a larger mechanical disadvantage but with every engine stroke, the locomotive is moved farther down the track. This is fine for a load of passengers where speed is important.  The next time you pedal your bike look at the front derailleur.  You are playing the same game.  You shift the chain to the large sprocket (on the gears by the pedals) when you want to go fast and move the chain to the smaller sprocket if you need to go uphill. 

Machines

1. What can you do to increase the mechanical advantage of a ramp or wedge?
   
   Simply alter the ramp so it has a lower slope (less steep incline).  You may exert a force over longer distance but the force required will be less.  You can probably guess this answer from everyday experience.  I love to bike but when I have to lift my own weight up a steep slope, it is not so much fun.
    
2. How can one easily calculate the mechanical advantage in a system of gears?
   
   If you count the number of teeth in each gear and divide (output /input), you get the MA. 
    

3. Which screw provides the highest mechanical advantage? Explain!
   
   The MA of a screw depends on the number of threads per inch.  The closer the threads, the higher the MA.  The screw depicted on the left has a higher MA.  You can think of a screw as a ramp shaped in a spiral.  If you understood the answer to question #1, you should see that the closer the threads, the gentler the slope.  The screw on the left is much easier to drive into a block of wood (but may take twice the number of turns to go in the wood to the same depth).    One student pointed out that the screw on the left looked much like the kind used for metal and the one on the right was for wood.  They reasoned that since it is much harder to drive any screw into metal than into wood, the left one probably had the greater mechanical advantage.  I don't know that much about screws but I certainly liked that answer.

4. What is a ratchet and pawl? What is its function?  Attach an image, or find a web page with an image. Give one common application.
   
   
   A ratchet and pawl is a gear where the teeth are slanted and a "stop" that only allows motion in one direction. If you have a winch, you have seen this in action.  You hear the click - click - click as you pull your boat on the trailer.  If you let go of the handle, the boat does not slide back into the water.  Most socket wrenches have one of these gizmos inside.

Compound Machines

Too numerous to mention but here are a few:

Bottle Jack - uses levers and hydraulics to lift a car
C-Clamp - uses a screw and lever
Bicycle - uses levers (for pedaling) and gears
 

One thing many student mention is a wheelbarrow. However, this is only a second class lever.  The wheel offers no mechanical advantage so it is not considered a simple machine (despite what many web pages might claim).

History of Technology

Tesla - No one on the web has a better biography of Tesla than this site.  http://www.teslauniverse.com/nikola-tesla-timeline-1856-birth-of-tesla  No question ... the accomplishments of Tesla has one of the biggest impacts on our lives.  After all, think of how dependent we are on electricity.  He not only established AC current as the standard we use today, but also invented the induction motor to put that electricity to work.

Discovery by accident - Please click here to see a list

Ancient Inventions - Here is a short list of things we use today but have been around for over 2000 years (besides the computer known as the Antikythera mechanism, which I listed in the original question).  I've clipped a few rather interesting posts (from students) for you to enjoy

Writing is the greatest of ancient discoveries (invention). Things like the Dispilio Tablet (https://en.wikipedia.org/wiki/Dispilio_Tablet) took us from a species of doers to a species of growers. Instead of doing what our ancestors had always done, a firm historical reference was started for the future generations of humans to learn and grow from. It has enabled everything from story telling to real learning institutions that have created some of the great minds of human history. Without writing, we would not be where we are today. Not even close. 

Amplifier (Bronze Urns)
Aqueducts
Calendars
Candles
Compass
Decoding Device, Greece, 5th Century BCE
Eyeliner
Helmets
Lighthouses
Locks
Machines (China)
Mirrors
Musical Instruments
Odometer
Parachute
Paper
Soap
Scissors
Toilets (that flush)
Umbrellas

You can find more at http://www.smith.edu/hsc/museum/ancient_inventions/ or http://listverse.com/2009/03/29/top-10-ancient-inventions-you-think-are-modern/

Here is a great video (part 1/5) - Ancient Discoveries (Machines of the Gods) here.

Obsolete Technologies  - Here are some thoughts sent in by students

• Wires for home networking (being replaced by wireless)
• Music and videos on a disk (in favor of streaming)
• Desktop computers (in favor of tablets, smart phones, notebooks/laptops)
• Land lines for phone service (cell phones everywhere now)
• Printed media (especially newspapers and magazines and even books) in favor of digital media
• Commercials on TV (since many shows are recorded and we skip ads) being replaced by product promotions within the shows themselves (remember Reeces Pieces in the movie ET?)
• Paper money, checks, and even credit cards (now you can pay by phone, auto pay online, etc)

Technological Wonders (really big technological projects/devices) - Here is my short list but anything big will work for me

Landing a man on the moon (covered in the introduction)
Computers and the Internet (covered in the introduction)
The Manhattan Project (the quest to build an atomic bomb) which ultimately ended the second world war.
The Large Hadron Collider - Smashing subatomic particles at CERN led to the discovery of the Higgs Boson
The ISS - An orbiting lab the size of a football field helped us study the Earth as well as properties of a zero g environment
The Hubble Space Telescope - Opened a new window to the universe
The James Webb Space Telescope - The successor to Hubble still set to launch
Rovers on Mars - Wow, we can explore another world from our rocking chairs at home