Question 1

Suppose a soap box car is coasting on a track (no motor; no brake), moving from left to right, and part of the track is shown below. Friction /air resistance is not present and the car is almost stopped, barely moving at point E.
 
-What must be true of the car's motion at point A?

Accepted Answer

The answer of Suppose a soap box car is coasting...

Question 2

Suppose a soap box car is coasting on a track (no motor; no brake), moving from left to right, and part of the track is shown below. Friction /air resistance is not present and the car is almost stopped, barely moving at point E.
 
-Please identify points of maximum and minimum kinetic energy, if any.

Accepted Answer

The answer of Suppose a soap box car is coasting...

Question 3

You are swinging a 2 kg tin can around your head in a perfectly horizontal circle of radius 1 m with a speed of 6 m/s. (This is really not possible but we're saying it almost happens.) If the string can safely exert a force of 30 N will it be able to swing the can?

Accepted Answer

A)  No because the required force is 36 N. 
B)  No because the required acceleration is 36 m/s2. 
C)  Yes because only linear acceleration would break the string. 
D)  Yes because the weight of the can does not matter.

Question 4

The coefficient of restitution for a particular ball is 0.7. If he ball rebounds from surface traveling at 60 m/s its collision speed was

Accepted Answer

A)  42 m/s 
B)  53 m/s 
C)  85.7 m/s 
D)  85.7 m/s2

Question 5

Explain why it is so difficult to ride a bicycle in tall grass or soft sand.

Accepted Answer

The answer of Explain why it is so difficult to...

Question 6

Bolts work because they act like very strong springs and extend slightly when they are tightened. Suppose a steel bolt has spring constant 1.8x108 N/m. How far would it have to stretch in order to provide a force 2000N?

Accepted Answer

A)  1.8x10-3 m 
B)  1.8x10-8 m 
C)  1.11 m 
D)  1.11x10-5 m

Question 7

Consider an elastic ball that is falling downward toward the ground. The ball hits the ground and then begins traveling upward again. At what point in the trip does the ball have the most energy stored in it as elastic potential energy?

Accepted Answer

A)  At the bottom of the path when it is not moving, right before it rebounds. 
B)  After it has rebounded and left the ground. 
C)  Right before it hits the ground 
D)  When it is moving the fastest.

Question 8

You are swinging a tin can around your head in a perfectly horizontal circle of radius 4 m. (This is really not possible but we're saying it almost happens.) If the speed of the can is 4 m/s what is its acceleration?

Accepted Answer

A)  1/4 m/s2 
B)  4 m/s2 
C)  16 m/s2 
D)  4 m/s

Question 9

You go to an amusement park and, being in a physics class, you have connections. The management lets you stand on a scale as you ride a Ferris Wheel that rotates fairly rapidly. You will notice the highest reading on the scale

Accepted Answer

A)  on top, because the normal force upwards is weaker than your weight. 
B)  on top, because the normal force upwards is stronger than your weight 
C)  on the bottom, because the normal force upwards is weaker than your weight. 
D)  on the bottom, because the normal force upwards is stronger than your weight.

Question 10

The curves on bicycle racetracks are steeply banked, so that the inner edge of each curve is much lower than its outer edge. This banking tips the support force that the track exerts on the bicycle wheel toward the center of each turn. That center-directed or centripetal force on the bicycle is important because it

Accepted Answer

A)  helps the bicycle accelerate inward to complete each turn without skidding. 
B)  it does work on the bicycle during each turn and thus increases the bicycle's energy. 
C)  balances the outward centrifugal force that the bicycle experiences as it completes each turn, so that the bicycle experiences zero net force. 
D)  it does negative work on the bicycle during each turn and thus decreases the bicycle's energy.

Question 11

You are riding an amusement park ride where you are strapped to the inside of a giant metal wheel that is rotating quite rapidly. Your acceleration is

Accepted Answer

A)  Zero 
B)  Straight down 
C)  Toward the center 
D)  Straight up

Question 12

Suppose you are standing on a bathroom scale when you are flying in a jet airplane. For a moment the scale reads more than your actual weight. During that moment, it's exerting an upward force on you that is greater than your weight and you are

Accepted Answer

A)  accelerating upward. 
B)  accelerating downward. 
C)  not accelerating. 
D)  accelerating sideways.

Question 13

You are riding a very fast Ferris Wheel so that you actually notice a variation in your apparent weight. Where is your apparent weight maximum?

Accepted Answer

A)  At the top 
B)  At the bottom 
C)  Halfway up, going down 
D)  Halfway up, going up

Exam 3: Mechanical Objects, Part 1

Suppose a soap box car is coasting on a track (no motor; no brake), moving from left to right, and part of the track is shown below. Friction /air resistance is not present and the car is almost stopped, barely moving at point E. -What must be true of the car's motion at point A?

Suppose a soap box car is coasting on a track (no motor; no brake), moving from left to right, and part of the track is shown below. Friction /air resistance is not present and the car is almost stopped, barely moving at point E. -Please identify points of maximum and minimum kinetic energy, if any.