Think Think Think Think Think Think Think Think Think Think Think Think Think

THINK THINK THINK THINK THINK THINK THINK THINK THINK THINK THINK THINK THINK GES 101 Exam 2 Take Home Name ______Fall 2011 Date ______

1. Suppose a strong wind (means a high wind speed) is blowing against your house today but just yesterday the wind was only half as much (means blowing at half the speed of today). Today, with the high wind speed your house seems like it’s going to fall apart and you wonder how much force the high speed wind exerts on your house as compared the low speed wind. Explain the physics you would use to find the ratio of the force for the high speed wind to the force of the wind at half that speed and then determine the value of that ratio.

2. Ok, for the same change in wind speed of the previous question, you wonder just how much more energy the wind carries at the high speed compared to half that speed. Explain the physics needed to answer this question and then find and display the ratio.

3. Now it is time for some exercise! You are on the track with your tennie-runners on and you start to run from rest. As you run you put a certain amount of momentum into yourself and also into the ground. Question is, “how do those two values compare?” State the physics you will need to use to answer this question and then give the answer.

4. But then you wonder, “how about the energy; how does the energy I put into myself compare to the energy I put into the ground?” You know what to do – clearly state the physics of how you will determine the answer to this question and then answer it.

1 THINK THINK THINK THINK THINK THINK THINK THINK THINK THINK THINK THINK THINK GES 101 Exam 2 Take Home Fall 2011

5. We’re on a roll, but now, after working up such a sweat a nice swim to cool down sounds good. You are in the water (without your tennie-runners of course - swimsuit optional) and you start to swim from rest. Again, you put a certain amount of momentum into yourself and also a certain amount into the water, but how do they compare? Gotta give me the physics you will need to determine how they will compare and then answer the question.

6. Well, now let’s compare the amount of energy you put into yourself here versus the amount you put into the water. Show the physics you will need to make this comparison and then work it out.

7. Suppose Sammy sharpshooter has two rubber bullets of exactly the same size, speed and mass 'cept one is made of rubber(it bounces!) and the other is made of putty (it does not bounce). Sammy shoots each bullet at a block of wood, say an eight inch by eight inch by fourteen inches high hunk of pine. Which bullet is the most likely to knock the block over? Give the physics to justify your answer.

8. Suppose you have two identical lumps of well chewed, nice and juicy grape flavored bubble gum. One is just sitting there doing nothing (nor is it stuck to the table) and you fling the other one at it with some speed, V. The two lumps collide, stick together (no, they still don't stick to the table) and become a single lump with twice the mass. You need to determine the speed of the double mass lump. What physics will you need to use and what is the final speed of the gum?

9. For the same sticky mess above, what proportion of the kinetic energy in the originally moving lump is turned into heat as a result of the collision? You know you must first give the physics and then find the answer.

10. Suppose you are pulling three blocks across a flat, smooth table with a force F as shown in the figure. The mass of block C is m, that of block B is 3m and that of block A is m. You are going to show the force diagram for each of the blocks separately and then for the system consisting of all of the blocks together.

Then you must show the physics of how you will determine the acceleration of the whole system and the tension in each of the massless, unstreachable connection cables.

11. A 1 kg mass is balanced as shown. You are going to determine the mass of the measuring stick. a. What physics would you use to find the mass of the measuring stick? TELL IT ALL!

b. What is the mass of the measuring stick if it is balanced by a support force at the 2/7 mark? SHOW ALL YOUR WORK!

12. For the following question, you must give correct logical and Physics reasons to get full credit. If you give incorrect physics, even if you guess the correct answer, it will not count. Be brief - our shorthand notation works just fine; if it is correct. You can write all over the figure if you want but only the ANSWERS will be graded. This question uses a good bit of the physics we studied so far. Read the information carefully.

A Hugh Car(HC) and a Little Tiny Car(LTC) are initially at rest on a horizontal parking lot at the edge of a steep cliff. For simplicity, we assume that HC has twice as much mass as LTC. Equal and constant forces are applied to each car and they accelerate across equal distances to the cliff. We ignore the effects of friction. When they reach the far end of the lot, the force is suddenly removed, whereupon they sail through the air and crash to the ground below.

CIRCLE YOUR CHOICE a Which car has the greater acceleration? HC LTC SAME WHY?

b Which car spends more time along the surface of the lot? HC LTC SAME WHY?

c Which car has the larger impulse imparted to it by the applied force? HC LTC SAME WHY?

d Which car has the greater momentum at the cliff’s edge? HC LTC SAME WHY?

e Which car has the greater work done on it by the applied force? HC LTC SAME WHY?

f Which car has the greater kinetic energy at the edge of the cliff ? HC LTC SAME WHY?

g Which car spends more time in the air, from the edge of the cliff to the ground below? HC LTC SAME WHY?

h Which car lands farthest horizontally from the edge of the cliff onto the ground below? HC LTC SAME WHY?

13. Ok, this question covers about all of the rotational physics we covered. Two forces are applied to a merry- go-round with a radius of 1.5 m as shown in the diagram. One force has a magnitude of 90 N and the other a magnitude of 60N. a. What is the torque about the axle of the merry-go-round due to the 90-N force? (call ccw positive) b. What is the torque about the axle due to the 60-N force? c. What is the net torque acting on the merry-go-round? d. If the mass of the merry-go-round is 120 kg, what is its angular acceleration (Treat the merry-go-round as a disk with rotational inertia given by I = 1/2MR2.) e. If the torques are applied for 30 s, what will be the final angular velocity of the merry-go-round? f. What will be the final angular momentum? g. What will be the final rotational kinetic energy? h. How much work was done in the 30 seconds? a.