### Fall 2003 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 105. The exam period was 90 minutes; the mean score was 78.1; the median score was 81. 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.

Sarah goes for a walk along the x-axis. The walk takes her 400 seconds to complete. The graph shows her velocity V as a function of time.

How far did Sarah walk in 400 seconds?

(a)   0 m
(b)   200 m
(c)   400 m
(d)   500 m
(e)   800 m

### QUESTION 2*

What was the maximum of the magnitude of her acceleration during the walk?

(a)   0.01 m/s2
(b)   0.02 m/s2
(c)   0.05 m/s2

### QUESTION 3*

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

This figure shows an airport luggage carrying train with a tractor T is pulling three luggage carts, M1, M2 and M3, with an acceleration of 1.4 m/s2. The mass of the tractor T is MT = 300 kg; the masses of the carts are M1 = 200 kg, M2 = 100 kg and M3 = 100 kg, respectively.

The net force on cart M3 is

(a)   140 N.
(b)   280 N.
(c)   560 N.

### QUESTION 4***

The net force on cart M2 is

(a)   140 N.
(b)   280 N.
(c)   560 N.

### QUESTION 5**

The force in the connection between the tractor T and cart M1 is

(a)   980 N.
(b)   560 N.
(c)   280 N.
(d)   40 N.
(e)   0 N

### QUESTION 6*

If the tractor starts from rest at time t = 0, how far has it moved after 10 seconds?

(a)   70 m
(b)   135 m
(c)   180 m

### QUESTION 7*

If the tractor starts from rest at time t = 0, how fast is it moving after 10 seconds?

(a)   7 m/s
(b)   14 m/s
(c)   21 m/s

### QUESTION 8***

What is the minimum coefficient of friction between the tractors wheels and the ground?

(a)   0.14
(b)   0.25
(c)   0.33

### QUESTION 9*

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

Two masses are suspended by a cord that passes over a pulley with negligible mass. The cord also has negligible mass. One of the masses, m1, has a mass of 5.0 kg and the other mass, m2, is unknown. The acceleration of m1 is measured to be 2.45 m/s2 downward.

Compare the magnitude of the tension in the string attached to m1 with that attached to m2.

(a)   |T1| > |T2|
(b)   |T1| = |T2|
(c)   |T1| < |T2|

### QUESTION 10**

The tension in the cord attached to m1 is

(a)   12.25 N
(b)   36.8 N
(c)   49 N

### QUESTION 11**

The mass of m2 is

(a)   2.0 kg.
(b)   3.0 kg.
(c)   4.0 kg.
(d)   5.0 kg.
(e)   6.0 kg.

### QUESTION 12*

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

Two masses are connected by a cord that passes over a pulley as shown in the figure. The pulley and the cord have negligible mass. Mass 2 moves on a horizontal surface without friction and mass 1 is suspended vertically. The cord has negligible mass. Mass 1 is equal to 4.0 kg and mass 2 is equal to 8.0 kg.

What is the acceleration of mass 1?

(a)   2.61 m/s2
(b)   3.27 m/s2
(c)   3.77 m/s2

### QUESTION 13*

What is the tension in the cord that connects the two masses?

(a)   15.2 N
(b)   21.2 N
(c)   26.2 N
(d)   32.7 N
(e)   37.7 N

### QUESTION 14*

Let T be the answer to the previous question. If the mass of both blocks were doubled, the tension in the cord would be

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

### QUESTION 15*

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

A ball is thrown horizontally outward from the balcony of a tall building. The ball starts 150 m above level ground. The initial speed of the ball is 35 m/s in the horizontal direction.

How much time does it take for the ball to reach the ground?

(a)   2.6 s
(b)   4.3 s
(c)   5.5 s

### QUESTION 16*

What is D, the distance between the building and where the ball lands?

(a)   D = 127 m
(b)   D = 194 m
(c)   D = 300 m
(d)   D = 378 m
(e)   D = 481 m

### QUESTION 17**

The speed of the ball just before the ball hits the ground is

(a)   35 m/s
(b)   50 m/s
(c)   64 m/s
(d)   91 m/s
(e)   101 m/s

### QUESTION 18*

A second identical ball is thrown from the balcony with a smaller horizontal speed. The time taken for the second ball to reach the ground is

(a)   the same as that for the first ball.
(b)   larger than that for the first ball.
(c)   smaller than that for the first ball.

### QUESTION 19*

This and the following question concern the same physical situation.

A small ball of mass m = 0.050 kg is suspended by an ideal string of length L = 0.40 m. and set in a circular motion. The cord makes an angle of θ with respect to the vertical. The constant angular velocity of the ball is ω = 5.50 radians/sec.

What is the speed of the ball?

(a)   ω L tanθ
(b)   ω L cosθ
(c)   ω L sinθ

### QUESTION 20**

What is the value of the tension in the string?

(a)   T = m g / tanθ
(b)   T = m g / cosθ
(c)   T = m g / sinθ

### QUESTION 21**

A block is pushed in the positive direction along a rough horizontal surface at a constant velocity v. The net force on the block is

(a)   zero.
(b)   equal to the force of friction.
(c)   greater than the force of friction.

### QUESTION 22**

A 4-kg picture is hung by two strings of equal length. Each string makes an angle of θ = 60° with the horizontal as shown in this figure. What is the tension T1?

(a)   T1 = 45.3 N
(b)   T1 = 39.2 N
(c)   T1 = 27.4 N
(d)   T1 = 22.7 N
(e)   T1 = 18.9 N

### QUESTION 23*

A person is standing on a scale in an elevator as the elevator is going up and slowing down. The reading on the scale is

(a)   smaller than when the elevator is at rest.
(b)   the same as when the elevator is at rest.
(c)   larger than when the elevator is at rest.

### QUESTION 24*

A 150 newton box is sliding down an incline at constant velocity. The surface of the incline has a coefficient of kinetic friction of 0.2. What is the angle θ of the incline as shown in this figure?

(a)   θ = 11.3°
(b)   θ = 9.5°
(c)   θ = 8.3°
(d)   θ = 7.7°
(e)   θ = 6.2°

### QUESTION 25*

A car travels for 140 km at 70 km/hr. It then travels an additional distance of 60 km 40 km/hr. The average speed of the car is

(a)   61.0 km/hr.
(b)   57.1 km/hr.
(c)   53.3 km/hr.
(d)   46.7 km/hr.
(e)   45.0 km/hr.

### QUESTION 26*

As you hurry to catch your flight at O’Hare Airport, you encounter a moving walkway that is 100 m long and has a speed of 2.5 m/s relative to the ground. If it takes you 80 seconds to cover 100 m when walking on the ground, how long will it take you to cover the same distance on the walkway? Assume that you walk with the same speed on the walkway as you do on the ground.

(a)   53 sec
(b)   40 sec
(c)   27 sec

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.