Question 1

You're riding on a pogo stick-a vertical stick with a spring at the bottom and foot pads on which you stand. You're holding the top of the stick tightly in your hands and you and the stick are bouncing up and down on its spring. As you land after one particularly high bounce, the spring becomes more and more tightly compressed. When the spring is at half its maximum compression, your velocity is

Accepted Answer

A)   downward but your acceleration is upward.
B)   upward and you acceleration is downward.
C)   (
A)   or (
B)  
D)   upward but your acceleration is upward. A

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 potential energy, if any.

Accepted Answer

The maximum potential energy is at A, E and the minimum is at B,D.

Question 3

You are swinging a tin can around your head in a perfectly horizontal circle and its acceleration is 32 m/s2. If its speed is 4 m/s what is the value of the radius of its circular path?

Accepted Answer

A)   4 m
B)   0.5 m
C)   0.5 m/s2
D)   2 m B

Question 4

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 lowest 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 5

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 present and the car comes to a stop at point E.
 
-Please identify points of maximum and minimum potential energy, if any.

Accepted Answer

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

Question 6

Imagine that you are able to go on a fishing trip that you have always wanted to. Your friend gets a bite that exerts a force of about 50N on the pole and it bends by a certain amount. Now you have a pole identical to your friends and you get a hit that bends the pole about twice as much. You can estimate that the force on your pole is about

Accepted Answer

A)   Can't tell
B)   100 N
C)   200 N
D)   500 N

Question 7

You have watched one too many old cartoons and decide to drive around town with a giant spring that is 4 m long and attached to the front of your car. You decide to help a semi truck that is stuck and try to push them with your car. You take a running start, and when you contact the truck the spring in your car compresses 3 m. During which portion of the compression did you do the least work on the spring?

Accepted Answer

A)   During the second meter.
B)   During the third meter.
C)   During the first meter.
D)   The work done is equal for all segments of the trip.

Question 8

A ball hits a wall going 10 m/s, and bounces off going 7 m/s. The coefficient of restitution is

Accepted Answer

A)   1.41
B)   0.70
C)   0.49
D)   -17 m/s

Question 9

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

Accepted Answer

A)   greater than your weight
B)   equal to zero
C)   equal to your weight.
D)   less than your weight.

Question 10

Suppose that a frantic weather reporter is covering a live tornado. It is in the mature stage just ripping right along and the reporter exclaims that "Wood, metal and all kinds of debris are being thrown directly outward from the edge the funnel." From a physics point of view (circular motion!) please comment on the accuracy of the reporter's statement.

Accepted Answer

The answer of Suppose that a frantic weather reporter is...

Question 11

A person is swinging a tin can around in a vertical circle at a constant speed. Please identify the points, if any, of
-maximum/ minimum potential energy

Accepted Answer

The answer of A person is swinging a tin can...

Question 12

Some engineers have suggested that we can simulate gravity in outer space by having a circular rotating space station where persons feel an outward - directed fictitious force due to the rotation of the station. The reason they feel such a force is because

Accepted Answer

A)   their velocity is toward the center of the space station and their inertia tends to keep them moving outward.
B)   the fictitious force is always in the direction of centripetal acceleration.
C)   they are accelerating toward the center of the space station and inertia tends to keep them moving sideways.
D)   their velocity is away from the center of the space station and their inertia tends to make them move in towards the center.

Question 13

You are flying on an airplane and you notice that a ball of aluminum foil from lunch starts to roll to the left. From the motion of the foil ball you can conclude that the plane is

Accepted Answer

A)   moving at constant velocity toward the right.
B)   turning toward the left.
C)   moving at constant velocity toward the left.
D)   turning toward the right.

Question 14

You are watching a semi truck bounce up and down on a spring. (Yep it's a toy!) At the topmost point in the truck's path,

Accepted Answer

A)   the truck's velocity is downward but its acceleration is upward.
B)   the truck's velocity is zero but its acceleration is upward.
C)   the truck's velocity is upward but its acceleration is downward.
D)   the truck's velocity is zero but its acceleration is downward.

Question 15

Cars are designed so that their bodies buckle (permanently deform) when they are in an accident. How does the buckling make the car safer by not allowing it to recoil (bounce) so much?

Accepted Answer

A)   The buckling stores energy.
B)   The buckling dissipates the energy of the crash.
C)   The buckling provides energy to the crashing objects.
D)   The buckling gives the car a high coefficient of restitution.

Question 16

When you throw a tennis ball against the floor at an angle,

Accepted Answer

A)   the direction of the vertical component of its velocity reverses.
B)   the horizontal component of its velocity reverses.
C)   the speed of the ball reverses.
D)   the vertical component of its velocity doubles.

Question 17

Which system is in a state of stable equilibrium?

Accepted Answer

A)   A marble in the bottom of a spherical bowl.
B)   A Marble on top of a spherical bowl.
C)   A marble on a flat, level surface.
D)   A marble rolling down an inclined surface.

Question 18

Assuming there is nothing wrong with your bathroom scale, discuss two ways in which you could get a false reading when weighing yourself, with only you touching the top of the scale (and nothing else) and another surface touching its bottom.

Accepted Answer

The answer of Assuming there is nothing wrong with your...

Question 19

When a baseball player hits a ball with the bat, the bat can undergo many different types of changes. Please discuss three different types of effects that contact with the ball has on the bat.

Accepted Answer

The answer of When a baseball player hits a ball...

Question 20

You thoughtfully set a 1 kg box on top of a loaf of bread and the loaf compresses by 15 cm. Thinking of the bread as a spring, its spring constant is

Accepted Answer

A)   1 N/m
B)   0.653 N/m
C)   65.3 N/m
D)   0.015 N/m

Exam 3: Mechanical Objects, Part 1

You are swinging a tin can around your head in a perfectly horizontal circle and its acceleration is 32 m/s². If its speed is 4 m/s what is the value of the radius of its circular path?