Spring 2004 Physics 101 Hour Exam 1(26 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 107. The exam period was 90 minutes; the mean score was 74.6; the median score was 76. Click here to see page1 page2 of the formula sheet that came with the exam.

QUESTION 1**

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

Three blocks are being accelerated upward by a force F applied to the bottom block as shown in the diagram. The mass of the bottom block is 7 kg, the mass of the middle block is 14 kg, and the top block is 21 kg.

Compare the net force on the bottom block F1 with the net force on the top block F3.

(a)   F1 < F3
(b)   F1 = F3
(c)   F1 > F3

QUESTION 2**

Calculate the net force on the top block

(a)   +546 N
(b)   +206 N
(c)   +134 N
(d)   +67.2 N
(e)   +44.8 N

QUESTION 3***

Calculate the force F applied to the bottom block as shown in the picture.

(a)   F = +546 N
(b)   F = +206 N
(c)   F = +134 N
(d)   F = +67.2 N
(e)   F = +22.4 N

QUESTION 4**

Calculate the net force on the middle block.

(a)   273 N
(b)   206 N
(c)   134 N
(d)   67.2 N
(e)   44.8 N

QUESTION 5*

This and the following question concern the same physical situation.

This velocity vs. time graph represents the motion of a car:

What was the acceleration of the car at t = 15 s ?

(a)   -2 m/s2
(b)   -1 m/s2
(c)   0 m/s2
(d)   1 m/s2
(e)   2 m/s2

QUESTION 6*

What was the displacement of the car between t = 0 s and t = 40 s ?

(a)   0 m
(b)   200 m
(c)   250 m
(d)   350 m
(e)   550 m

QUESTION 7*

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

Two blocks are connected by a string over an ideal massless pulley suspended from the ceiling as shown in the diagram. At the instant shown, the tension in the string T = 15 N.

Calculate the magnitude of the acceleration of the 2.5 kg block.

(a)   a = 3.8 m/s2
(b)   a = 6.0 m/s2
(c)   a = 16 m/s2

QUESTION 8**

As the large block falls and its speed increases, the tension T in the string

(a)   increases.
(b)   remains constant.
(c)   decreases.

QUESTION 9***

What is the net force F needed to support the pulley at the instant shown in the picture?

(a)   F = 15 N
(b)   F = 30 N
(c)   F = 35 N

QUESTION 10**

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

Two identical blocks (M = 1.5 kg) are being pulled across a frictionless surface by ropes. The magnitude of the tension in each of the ropes is the same, (T = 15 N) but, the force on block one is horizontal, and the force on block two is 45° above horizontal.

Compare the magnitude of the net force on block 1, with the magnitude of the net force on block 2.

(a)   F1 < F2
(b)   F1 = F2
(c)   F1 > F2.

QUESTION 11***

Compare the vertical component of the net force on block 1, with the vertical component of the net force on block 2.

(a)   F1y < F2y
(b)   F1y = F2y
(c)   F1y > F2y

QUESTION 12**

Block 2 reaches a part of the surface with friction (μ = 0.78). Calculate the acceleration of block 2 as it is pulled across this surface by a force of 15 N applied 45° above horizontal.

(a)   2.1 m/s2
(b)   4.9 m/s2
(c)   9.7 m/s2

QUESTION 13*

This and the following question concern the same physical situation.

A ball is thrown vertically up into the air.

At the moment it reaches its maximum height, the acceleration of the ball is (note positive acceleration is up, negative down).

(a)   a < 0
(b)   a = 0
(c)   a > 0

QUESTION 14*

At the moment it reaches its maximum height, the velocity of the ball is (note positive velocity is up, negative down).

(a)   v < 0
(b)   v = 0
(c)   v > 0

QUESTION 15**

This and the following question concern the same physical situation.

A 100 kg box is sliding down on an incline with an acceleration of 2 m/s2. The angle α of the incline is 30°.

What is the kinetic friction coefficient between the box and the incline?

(a)   1.74
(b)   0.80
(c)   0.34
(d)   0.30
(e)   0.12

QUESTION 16**

If we increase the mass of the box the acceleration will

(a)   increase.
(b)   stay the same.
(c)   decrease.

QUESTION 17**

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

A ball is fired by a cannon at an angle θ = 30° above horizontal with initial speed Vo = 300 m/s.

At what distance S will the ball hit the ground?

(a)   S = 9184 m
(b)   S = 7953 m
(c)   S = 4592 m
(d)   S = 15096 m
(e)   S = 3976 m

QUESTION 18*

What is the maximum altitude h of the ball?

(a)   h = 4591 m
(b)   h = 3443 m
(c)   h = 1148 m

QUESTION 19**

What is the speed of the ball at the highest point of the trajectory of the ball?

(a)   300 m/s
(b)   260 m/s
(c)   150 m/s

QUESTION 20**

Unfortunately the target was located at a distance of a couple meters greater than S. Without changing the initial velocity of the ball, how should the artillery man adjust the angle θ to try to hit the target?

(a)   increase the angle θ
(b)   decrease the angle θ

QUESTION 21*

This and the following question concern the same physical situation.

A traffic sign hangs by two cables attached to two adjoining buildings as shown in the figure below. Cable A makes an angle of θ = 45° with the wall of the left-hand building. Cable B is horizontal.

What is the mass of the traffic sign if the tension in cable B, TB = 49 N ?

(a)   7.1 kg
(b)   5.0 kg
(c)   3.5 kg
(d)   12.3 kg
(e)   1.2 kg

QUESTION 22**

Let M be the answer to the previous question. If the mass of the sign is doubled to 2M and the angles stay the same, the tension in cable B would be

(a)   49 N
(b)   69 N
(c)   98 N

QUESTION 23*

This and the following question concern the same physical situation.

Moving at a constant speed, a 700 kg car completes one lap in 32 s around a flat circular track with radius 100 m.

What is the acceleration of the car?

(a)   15.42 m/s2
(b)   3.86 m/s2
(c)   zero

QUESTION 24*

What is the minimum coefficient of friction between the car and the track?

(a)   0.1
(b)   0.2
(c)   0.3
(d)   0.4
(e)   0.5

QUESTION 25**

This and the following question concern the same physical situation.

Two wheels A and B are connected by a belt C which does not slip. Wheel A is rotating with a frequency of 300 rpm. The radius of wheel A is RA = 50 cm and the radius of wheel B is RB = 18 cm, as shown in the figure below. (1 rpm = 1 revolution per minute)

What is the angular frequency of the wheel B?

(a)   833.3 rpm
(b)   1885 rpm
(c)   5236 rpm

QUESTION 26**

What is the linear speed of the belt?

(a)   11.2 m/s
(b)   13.3 m/s
(c)   15.7 m/s
(d)   17.1 m/s
(e)   19.5 m/s

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.