Spring 2005 Physics 101 Hour Exam 1(25 questions)

The grading button and a description of the scoring criteria are at the bottom of this page. Basic questions are marked by a single star *. More difficult questions are marked by two stars **. The most challenging questions are marked by three stars ***.

True-false questions are worth 2 points each, three-choice multiple choice questions are worth 3 points each, five-choice multiple choice questions are worth 6 points each. The maximum possible score is 108. The exam period was 90 minutes; the mean score was 81.5; the median score was 85. Click here to see page1 page2 of the formula sheet that came with the exam.

QUESTION 1*

This and the following question concern the same physical situation.

A 3 kg block is released from rest at the top of a frictionless ramp 1.5 meters long. The acceleration of the block is measured to be 3.8 m/s2.

What is the angle θ of the ramp?

(a)   θ = 12.1°
(b)   θ = 16.3°
(c)   θ = 22.8°
(d)   θ = 25.2°
(e)   θ = 37.4°

QUESTION 2*

How fast is the block going when it reaches the bottom of the ramp?

(a)   3.4 m/s
(b)   4.7 m/s
(c)   5.3 m/s

QUESTION 3**

This and the following question concern the same physical situation.

An elevator is traveling down toward the bottom floor at a rate of 3.8 m/s. As it nears the bottom floor, the brakes are applied and it slows down at a constant rate of 1.5 m/s2.

What is the apparent weight of a 55 kg person in the elevator while the brakes are being applied?

(a)   330 N
(b)   450 N
(c)   540 N
(d)   620 N
(e)   750 N

QUESTION 4*

How far does the elevator travel after the brakes are applied before coming to a stop?

(a)   2.6 m
(b)   3.7 m
(c)   4.8 m

QUESTION 5*

A person throws a ball straight up (positive y direction) in the air. Which one of the plots below best represents the velocity as a function of time while the ball is in the air?

(a)
(b)
(c)

QUESTION 6*

This and the following two questions concern the same physical situation.

A 3 kg block is connected to 5 kg block that is being pulled by a force to the right across a frictionless surface. The acceleration of the two blocks is observed to be 1.8 m/s2.

What is the magnitude of the tension T in the string connecting the two blocks?

(a)   5.4 N
(b)   9.0 N
(c)   14.4 N

QUESTION 7*

What is the magnitude of the force F pulling the 5 kg block to the right?

(a)   5.4 N
(b)   9.0 N
(c)   14.4 N

QUESTION 8*

What is the magnitude of the net force on the 5 kg block?

(a)   9.0 N
(b)   14.4 N
(c)   18.8 N

QUESTION 9**

Compare your weight on earth WE with your weight on another planet Wp that is ½ the radius of earth, and also ½ the mass of earth.

(a)   WE > WP
(b)   WE = WP
(c)   WE < WP

QUESTION 10**

A car is traveling 50 m/s when its brakes are applied bringing it to a stop in 85 meters. (Assume the acceleration is uniform). How much time does it take the car to stop?

(a)   1.7 s
(b)   3.4 s
(c)   5.1 s
(d)   6.3 s
(e)   7.2 s

QUESTION 11**

This and the following question concern the same physical situation.

Two blocks are connected by string over a massless frictionless pulley as shown in the figure to the right. Once released, the 7 kg block accelerates downward raising the 3 kg block up.

What is the acceleration of the 3-kg block?

(a)   2.9 m/s2
(b)   3.9 m/s2
(c)   6.9 m/s2
(d)   9.8 m/s2
(e)   14 m/s2

QUESTION 12**

Compare the |F3| the net force on the 3 kg block with |F7| the magnitude of the net force on the 7 kg block.

(a)   |F3| > |F7|
(b)   |F3| = |F7|
(c)   |F3| < |F7|

QUESTION 13**

This and the following question concern the same physical situation.

A box of mass M = 7 kg is pulled across a horizontal floor at constant velocity. There is friction between the box and the floor. As shown in the figure, the force F makes an angle θ = 64° with the horizontal and the friction coefficient between the box and the floor is μ = 0.1.

What is the magnitude of the normal force on the box compared to the weight of the box, Mg ?

(a)   smaller than Mg
(b)   equal to Mg
(c)   larger than Mg

QUESTION 14**

What is the magnitude of the force F ?

(a)   F = 5 N
(b)   F = 13 N
(c)   F = 27 N
(d)   F = 31 N
(e)   F = 44 N

QUESTION 15***

This and the following question concern the same physical situation.

A bird is resting on a phone wire between two poles that are 30 m apart. The bird is exactly midway between the two poles. Because of the weight of the bird, the wire sags by 50 cm. The tension in the wire is 70 N. (The mass of the wire is negligible.)

What is the mass of the bird?

(a)   121 g
(b)   232 g
(c)   365 g
(d)   476 g
(e)   554 g

QUESTION 16**

If the distance between the posts was 20 m, and the same bird was resting exactly midway between the two poles with the wire sagging by 50 cm, the tension in the wire would be

(a)   smaller than 70 N.
(b)   equal to 70 N.
(c)   larger than 70 N.

QUESTION 17*

This and the following three questions concern the same physical situation.

A car is going at constant speed, v = 45 m/s, on a circular race track. The radius of the track is R = 270 m.

How long does it take the car to travel one lap?

(a)   t = 18.8 s
(b)   t = 24.4 s
(c)   t = 37.7 s

QUESTION 18*

What is the magnitude of the centripetal acceleration of the car?

(a)   3.1 m/s2
(b)   4.2 m/s2
(c)   5.3 m/s2
(d)   6.4 m/s2
(e)   7.5 m/s2

QUESTION 19**

What is the minimum friction coefficient, μ, between the tires and the race track so that the car does not skid out of the race track?

(a)   μ = 0.53
(b)   μ = 0.61
(c)   μ = 0.77
(d)   μ = 0.89
(e)   μ = 0.93

QUESTION 20*

Let μ be the answer to the previous question. If the car was going faster than 45 m/s, the minimum friction coefficient between the tires and the race track so that the car does not skid out of the race track would be

(a)   smaller than μ.
(b)   equal to μ.
(c)   larger than μ.

QUESTION 21*

This and the following two questions concern the same physical situation.

Eddy throws a little sand bag so that it lands on the top of a vertical post that is 4 m high. The post is 1.3 m away from Eddy. He releases the bag from a height of 1.5 m above the ground, as shown in the figure. The initial speed of the bag is v = 7.5 m/s, the angle, θ, between the velocity and the horizontal is θ = 80°. You can neglect the friction due to the air.

How long does the sand bag stay in the air?

(a)   t = 0.7 s
(b)   t = 1.0 s
(c)   t = 2.5 s

QUESTION 22*

During its course in the air, the sand bag reaches a maximum height H, as depicted in the figure. Calculate H.

(a)   H = 4.3 m
(b)   H = 4.7 m
(c)   H = 5.2 m

QUESTION 23**

What is the speed of the bag just before it lands on the top of the post?

(a)   0.0 m/s
(b)   0.3 m/s
(c)   1.4 m/s
(d)   1.9 m/s
(e)   2.7 m/s

QUESTION 24*

This and the following question concern the same physical situation.

Tarzan is trying to cross a river that is flowing at a speed vriver. Jane is waiting for him on the other side of the river, exactly across from him. Tarzan swims at a speed of 4 m/s. He determines that in order to swim straight to Jane, he needs to swim at an angle θ = 22°, as shown in the figure.

What is the speed of the river?

(a)   vriver = 1.5 m/s
(b)   vriver = 2.6 m/s
(c)   vriver = 3.7 m/s
(d)   vriver = 4.8 m/s
(e)   vriver = 5.9 m/s

QUESTION 25*

If Tarzan takes 2 minutes to cross the river, what is the width of the river?

(a)   W = 100 m
(b)   W = 220 m
(c)   W = 350 m
(d)   W = 450 m
(e)   W = 510 m

Scoring of True-False (T,F) Questions:
• If you mark the correct answer, you get 2 points.
• If you mark the wrong answer or if you mark neither answer, you get 0 points.
Scoring of Multiple Choice I (a,b,c) Questions:
• If you mark the correct answer, you get 3 points.
• If you mark a wrong answer or if you mark none of the answers, you get 0 points.
Scoring of Multiple Choice II (a,b,c,d,e) Questions:
• If you mark one answer and it is the correct answer, you get 6 points.
• If you mark two answers and one of them is the correct answer, you get 3 points.
• If you mark three answers and one of them is the correct answer, you get 2 points.
• If you do not mark the correct answer, or if you mark more than three answers, or if you mark none of the answers, you get 0 points.