### Fall 1999 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 ***.

This exam consists of 25 questions; 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. When the exam was given, the minimum "A" score was 93; the minimum "B" was 81; the minimum "C" was 68; the minimum "D" was 52. The mean was 87.0; the median was 91. Click here to see the formula sheet that came with the exam.

### QUESTION 1*

The next four questions are about the following situation:

A bus makes a trip according to the position versus time graph shown to the right. The trip is composed of three separate segments, labeled A, B, and C.

In which of the segments is the speed of the bus the largest?

(a)   A
(b)   B
(c)   C

### QUESTION 2**

The average velocity of the bus over the full trip is zero.

(T)   True
(F)   False

### QUESTION 3*

The average acceleration during the time between 0.5 and 1.0 hours is zero.

(T)   True
(F)   False

### QUESTION 4*

Which of the following plots best represents the velocity of the bus as a function of time?

(a)
(b)
(c)

### QUESTION 5*

The next three questions are about the following situation:

At t = 0 a ball is thrown straight upward from the edge of a cliff with initial velocity 25 m/s. It lands on the ground at the base of the cliff 7 seconds later.

At what time is the ball at its maximum height?

(a)   t = 1.42 s
(b)   t = 2.55 s
(c)   t = 2.98 s
(d)   t = 3.56 s
(e)   t = 5.45 s

### QUESTION 6*

What is the height H of the cliff?

(a)   H = 46.2 m
(b)   H = 53.2 m
(c)   H = 65.3 m
(d)   H = 76.0 m
(e)   H = 82.1 m

### QUESTION 7*

What is the speed |v| of the ball as it hits the ground?

(a)   |v| = 12.2 m/s
(b)   |v| = 25.0 m/s
(c)   |v| = 43.7 m/s
(d)   |v| = 50.0 m/s
(e)   |v| = 55.2 m/s

### QUESTION 8*

The next three questions are about the following situation:

A cannon ball is fired at an angle of 22° above horizontal with an initial speed vo = 250 m/s, reaching a maximum height of h before hitting the ground. (You can neglect air resistance.)

What is the maximum height h reached by the ball?

(a)   h = 447 m
(b)   h = 782 m
(c)   h = 981 m
(d)   h = 2420m
(e)   h = 3185 m

### QUESTION 9*

Suppose the answer to the above problem is h. If the cannon is fired with an initial speed of 2vo, the maximum height reached by the ball is

(a)   2h
(b)   3h
(c)   4h

### QUESTION 10**

What is the y component of the ball's velocity, vy, just before it hits the ground?

(a)   vy = -250 m/s
(b)   vy = -94 m/s
(c)   vy = 0 m/s
(d)   vy = 94 m/s
(e)   vy = 250 m/s

### QUESTION 11*

A car is rolling down a hill and the driver is applying the brakes so that the car is traveling at a constant velocity. The net force on the car is zero.

(T)   True
(F)   False

### QUESTION 12*

Two cars are traveling toward each other in adjacent lanes of a straight road. One car is moving 25 m/s and the other 50 m/s. If the cars are initially 2000 m apart, how much time elapses before they meet.

(a)   12.5 s
(b)   26.7 s
(c)   40.0 s
(d)   51.3 s
(e)   80.0 s

### QUESTION 13*

An astronaut with mass MA = 75 kg pushes on a spacecraft giving herself an acceleration of 1.5 m/s2, and the spacecraft an acceleration of -2.8 x 10-4 m/s2. What is Ms the mass of the spacecraft?

(a)   Ms = 0.51 x 105 kg
(b)   Ms = 1.02 x 105 kg
(c)   Ms = 2.01 x 105 kg
(d)   Ms = 4.02 x 105 kg
(e)   Ms = 8.04 x 105 kg

### QUESTION 14***

A small and a large block (mass M and 2M respectively) are arranged on a horizontal surface as shown below. A student pushes on the left side of the small block so that the entire system accelerates to the right. How does the net force on the small block FS compare to the net force on the large block FL?

(a)   FS > FL
(b)   FS = FL
(c)   FS < FL

### QUESTION 15*

A ball is dropped from the window of a stationary train and hits the ground 3 seconds later. If the train were in motion when the ball was dropped, the time for the ball to hit the ground would be

(a)   less than 3.
(b)   more than 3.
(c)   3 seconds.

### QUESTION 16*

Two identical boxes, each having a weight W, are tied to the ends of a massless string which hangs motionless over a pair of pulleys (see picture). What is the tension T in the string?

(a)   T = 0
(b)   T = W
(c)   T = 2W

### QUESTION 17*

Suppose a box having a weight W sits on the floor of an elevator that is moving downward with constant velocity V. What is the magnitude of the normal force FN exerted by the elevator floor on the box?

(a)   FN < W
(b)   FN = W
(c)   FN > W

### QUESTION 18**

In the drawing to the right, a block of weight W hangs from one end of a massless string that is wrapped over a massless, frictionless pulley. The other end of the string is attached to a second block that is on a horizontal frictionless surface. The entire system is accelerating under the influence of gravity, which points downward. How does the tension T in the string compare with W?

(a)   T > W
(b)   T = W
(c)   T < W

### QUESTION 19*

A block of weight W is held in place against a vertical wall by an external force F and by static friction between the block and the wall, as shown in the figure below. What is the magnitude of the normal force N exerted on the block by the wall?

(a)   N = 0
(b)   N = F
(c)   N = W

### QUESTION 20**

Consider the following two ways of moving a box across a horizontal floor with constant velocity. In case 1, you are pushing on the box from an angle of 30° above horizontal, and in case 2 you are pulling on the box at an angle of 30° above horizontal (see pictures). Assuming that the coefficient of kinetic friction between the box and the floor is the same in both cases, in which case is the magnitude of the frictional force exerted on the box by the floor the greatest?

(a)   Case 1
(b)   Case 2
(c)   The frictional force is the same in both cases

### QUESTION 21*

The next three questions are about the following situation:

A 75kg box sits on a horizontal floor. Wanting to move the box, you apply a horizontal force to one side of it. You find you have to push with a force of at least 300 N before the box will start moving.

What is the coefficient of static friction mS between the box and the floor?

(a)   mS = 0.29
(b)   mS = 0.37
(c)   mS = 0.41
(d)   mS = 0.52
(e)   mS = 0.63

### QUESTION 22*

The coefficient of kinetic friction is mk = 0.20. If you keep pushing on the box with a horizontal force of 300 N after it starts moving, what is a, the magnitude of the box's acceleration?

(a)   a = 2.0 m/s2
(b)   a = 2.5 m/s2
(c)   a = 3.0 m/s2
(d)   a = 3.5 m/s2
(e)   a = 4.0 m/s2

### QUESTION 23**

After pushing on the box until it has a speed of 2 m/s, you suddenly stop pushing. How much further will the box slide before coming to rest?

(a)   0 m
(b)   0.51 m
(c)   1.02 m
(d)   1.51 m
(e)   2.76 m

### QUESTION 24*

The next two questions are about the following situation:

Car A has a mass of 1000 kg and is driving around a horizontal circular track that has a radius of 1500 m. The speed of the car is 45 m/s, and is constant.

The net force on the car:

(a)   Is zero.
(b)   Is pointing radially inward, toward the center of the circle.
(c)   Is pointing radially outward, away from the center of the circle.

### QUESTION 25*

What is the magnitude of the net force, FA, acting on car A?

(a)   FA = 0 N
(b)   FA = 1.35 x 103 N
(c)   FA = 2.41 x 103 N
(d)   FA = 5.92 x 103 N
(e)   FA = 7.80 x 103 N

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.