### Spring 2006 Physics 101 Hour Exam 1(24 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 103. The exam period was 90 minutes; the mean score was 85.0; the median score was 91. 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.

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

In which one of the segments is the speed of the car the largest?

(a)   A
(b)   B
(c)   C

### QUESTION 2**

The average velocity of the car 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 one of the following plots best represents the velocity of the car as a function of time?

(a)
(b)
(c)

### QUESTION 5**

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 6*

This and the following question concern the same physical situation.

A block is held by two strings as shown in the figure below. The string on the left is pulling horizontally and the string on the right pulls at an angle θ = 30° as shown. The tension in the right string is 320 N. (Gravity acts in the y direction.)

What is the tension in the left string?

(a)   TL = 320 N
(b)   TL = 320 cos(30°) N
(c)   TL = 320 sin (30°) N

### QUESTION 7*

What is the mass of the block?

(a)   M = 7.3 kg
(b)   M = 18 kg
(c)   M = 28 kg
(d)   M = 72 kg
(e)   M = 180 kg

### QUESTION 8*

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

A basketball player is shooting the basketball 10 meters from the hoop. He releases the ball when it is 2 meters above the floor, with an initial velocity of 12 m/s, at an angle of 65° above horizontal as shown in the picture.

How long does it take the ball to reach the hoop?

(a)   0.83 s
(b)   1.20 s
(c)   1.97 s

### QUESTION 9*

How high is the ball above the ground when it has traveled the distance of 10 m horizontally?

(a)   1.9 m
(b)   3.6 m
(c)   4.4 m

### QUESTION 10*

Calculate ymax the maximum height the ball reaches.

(a)   ymax = 6.8 m
(b)   ymax = 8.0 m
(c)   ymax = 8.5 m
(d)   ymax = 9.0 m
(e)   ymax = 9.5 m

### QUESTION 11*

How fast is the ball going when it is at its maximum height?

(a)   0 m/s
(b)   5.1 m/s
(c)   12 m/s

### 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*

Shortly after launching a rocket is a distance of 50 meters above the earth, traveling up at a speed of 22 m/s and accelerating up at a rate of 5 m/s2. What is the apparent weight of a 75 kg astronaut in the rocket? (Be careful, all three choices can be obtained using the numbers given in this problem!)

(a)   360 N
(b)   735 N
(c)   1110 N

### QUESTION 14*

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

At t = 0 a ball is thrown straight upward from the edge of a cliff with initial velocity V0 = 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 15*

What is the height H of the cliff?

(a)   H = 46 m
(b)   H = 53 m
(c)   H = 65 m
(d)   H = 76 m
(e)   H = 82 m

### QUESTION 16**

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

(a)   | v | = 12 m/s
(b)   | v | = 25 m/s
(c)   | v | = 44 m/s
(d)   | v | = 50 m/s
(e)   | v | = 55 m/s

### QUESTION 17**

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 while in the case 2 you are pulling on the box (see pictures).

Assuming that the coefficient of kinetic friction between the box and the floor is the same in both cases, how does the magnitude of the frictional force exerted on the box by the floor compare?

(a)   The frictional force in case 1 is larger than in case 2.
(b)   The frictional force in case 2 is larger than in case 1.
(c)   The frictional force is the same in both cases.

### QUESTION 18*

This and the following question concern the same physical situation.

A box of mass M slides down a frictionless inclined plane that makes an angle θ with the horizontal.

What is the magnitude of the normal force acting on the box?

(a)   M g
(b)   M g cos(θ)
(c)   M g sin(θ)

### QUESTION 19**

What is the magnitude of the net force acting on the box?

(a)   M g
(b)   M g cos(θ)
(c)   M g sin(θ)

### QUESTION 20*

A 10 kg box is sliding with constant velocity down a ramp that makes an angle of 10° with the horizontal. What is the magnitude of the frictional force between the ramp and the box?

(a)   7 N
(b)   17 N
(c)   34 N
(d)   98 N
(e)   103 N

### QUESTION 21*

A man swims across a river of width 75 m by swimming in the direction that will take him across in the smallest possible time. The river is flowing with a speed of 1.8 m/s. When he reaches the opposite shore, he has been swept 55 m downstream.

How fast did he swim relative to the water?

(a)   1.5 m/s
(b)   2.5 m/s
(c)   4 m/s
(d)   5 m/s
(e)   6 m/s

### QUESTION 22*

Three forces act on an object as shown in the figure below. (F2 points along the x direction and F3 points along the -y direction). What is the magnitude of the net force acting on the object?

(a)   366 N
(b)   535 N
(c)   677 N
(d)   1224 N
(e)   2000 N

### QUESTION 23*

This and the following question concern the same physical situation.

A block of mass M = 20 kg is at rest on a horizontal surface. It is pulled to the right with a force F. The minimum value of force needed to get the block sliding is 150 N. What is the value of the coefficient of static friction between the block and the surface?

(a)   0.45
(b)   0.52
(c)   0.62
(d)   0.77
(e)   0.81

### QUESTION 24*

If the block is pulled with a force 150.1 N, it has an acceleration to the right of 2.40 m/s2. What is the coefficient of kinetic friction between the block and the surface?

(a)   0.45
(b)   0.52
(c)   0.62
(d)   0.76
(e)   0.81

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.