### Spring 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 true-false questions worth 2 points each, traditional multiple-choice questions worth 3 points each, and enhanced multiple-choice questions worth 6 points each. The maximum possible score is 105. When the exam was given, the minimum "A" score was 92; the minimum "B" was 75; the minimum "C" was 57; the minimum "D" was 3. The mean was 73.6; the median was 75. Click here to see the formula sheet that came with the exam.

### QUESTION 1*

At the very top of the trajectory of a ball thrown straight up, the instantaneous acceleration of the ball is zero.

(T)   True
(F)   False

### QUESTION 2*

Two balls, A and B, are launched horizontally from the roof of a building at the same time. The initial speed of ball A is twice that of ball B. Neglecting air resistance and assuming the ground below is horizontal,

(a)   ball A hits the ground before ball B.
(b)   ball B hits the ground before ball A.
(c)   ball A and ball B hit the ground at the same time.

### QUESTION 3*

A projectile fired vertically upward at t = 0 reaches its maximum height at t = 10 sec. What is the maximum height ymax reached by the projectile?

(a)   ymax = 275 m
(b)   ymax = 490 m
(c)   ymax = 368 m
(d)   ymax = 608 m
(e)   ymax = 530 m

### QUESTION 4*

How high above the ground is the projectile in the above problem at t = 15 sec?

(a)   ymax = 275 m
(b)   ymax = 490 m
(c)   ymax = 368 m
(d)   ymax = 608 m
(e)   ymax = 530 m

### QUESTION 5**

An airplane is flying with a speed V with respect to the air. The nose of the aircraft points directly north according to a compass in the cockpit. The air itself (wind) is moving toward the west with the same speed V with respect to the ground (see picture below). The speed of the aircraft as measured by an observer on the ground is VG.

Which of the following is true:

(a)   VG = V
(b)   VG > V
(c)   VG < V

### QUESTION 6*

A student who can swim with a speed of 3 m/s in still water wants to get to the other side of a 400 m wide river whose waters flows downstream at 2 m/s. If she swims across in such a way that the time taken is the smallest possible, how far D is she swept downstream of the point on the opposite bank directly across from her starting point?

(a)   221 m
(b)   400 m
(c)   133 m
(d)   267 m
(e)   333 m

### QUESTION 7**

In the above situation, if she instead swims in such a way that her path as viewed by someone on the shore is straight across the river, how long does it take to get to the other side?

(a)   179 s
(b)   112 s
(c)   208 s
(d)   92 s
(e)   156 s

### QUESTION 8**

The net force on a car driving up a hill with constant velocity is zero.

(T)   True
(F)   False

### QUESTION 9***

A block starts from rest at t = 0 and slides down a ramp with constant acceleration. When t = 1 s, the block has traveled a distance D. What will be the distance traveled between t = 1 s and t = 2 s?

(a)   D
(b)   2D
(c)   3D

### QUESTION 10**

A block is released from rest at the top of a frictionless ramp (inclined plane) that makes an angle of 25° with respect to horizontal. At the bottom of the ramp, after having slid a distance D1, the speed of the block is observed to be 12 m/s. What is the length of the ramp D1?

(a)   8.9 m
(b)   11.8 m
(c)   13.7 m
(d)   15.2 m
(e)   17.4 m

### QUESTION 11**

In the above situation, what is the speed of the block when it is half-way down the ramp?

(a)   8.5 m/s
(b)   6.9 m/s
(c)   9.3 m/s
(d)   14.2 m/s
(e)   7.7 m/s

### QUESTION 12*

It is possible for a car to be moving toward the east while accelerating toward the west.

(T)   True
(F)   False

### QUESTION 13*

Car A accelerates from 15 to 30 mph in time Dt. Car B accelerates from 30 to 60 mph in the same time Dt. Which one of the following statements is correct?

(a)   The average acceleration of car A is less than the average acceleration of car B.
(b)   The average acceleration of car A is greater than the average acceleration of car B.
(c)   The average acceleration of car A is the same as the average acceleration of car B.

### QUESTION 14**

A daredevil is shot out of a horizontal cannon at the top of a 600 m high tower. Her initial velocity is 30 m/s in the horizontal direction. What is her speed when she reaches a height of 300 m above the ground?

(a)   108 m/s
(b)   94 m/s
(c)   65 m/s
(d)   70 m/s
(e)   82 m/s

### QUESTION 15***

An object always moves in the direction of the net force acting on it.

(T)   True
(F)   False

### QUESTION 16*

At a certain instant of time, the acceleration and velocity vectors of an object are as shown. Which statement most correctly describes the motion of this object?

(a)   Speed decreasing and turning upward.
(b)   Speed increasing and turning downward.
(c)   Speed constant and turning upwards.

### QUESTION 17*

A block of mass 50 kg is free to slide on a horizontal frictionless surface. A force F is applied as shown in the drawing, where the angle of the force above horizontal is 20°. As a result, the block has a horizontal acceleration of 4 m/s2. What is the magnitude of the applied force F?

(a)   124 N
(b)   343 N
(c)   180 N
(d)   367 N
(e)   213 N

### QUESTION 18**

A block of mass 50 kg is free to slide on a frictionless inclined plane that makes an angle of 20° with respect to horizontal. A force F is applied as shown in the drawing, this time pulling parallel to the plane. As a result, the block accelerates up the plane at 4 m/s2. What is the magnitude of the applied force F?

(a)   124 N
(b)   343 N
(c)   180 N
(d)   367 N
(e)   213 N

### QUESTION 19*

You are standing on a bathroom scale in an elevator that is moving up the Sears Tower. As the elevator slows down in order to stop at the top floor, the reading of the scale increases.

(T)   True
(F)   False

### QUESTION 20***

In this picture, a block rests on a frictionless table. Attached to the block is a string which passes over a frictionless pulley. A weight hangs from the other end of the string (see picture). Initially the top block is held at rest and the tension in the string is measured to be To. The block is then released. Which of the following characterizes the tension T in the string as the system accelerates after release?

(a)   T > To
(b)   T = To
(c)   T < To

### QUESTION 21**

An elevator of mass m = 1000 kg is pulled upward with constant acceleration a = 3.2 m/s2. Find the tension in the cable pulling the elevator up.

(a)   3.2 × 103 N
(b)   6.6 × 103 N
(c)   9.8 × 103 N
(d)   1.3 × 104 N
(e)   1.5 × 104 N

### QUESTION 22*

If the elevator in the above problem were instead pulled upward with a constant velocity of 3.2 m/s, what would the tension on the elevator cable be?

(a)   3.2 × 103 N
(b)   6.6 × 103 N
(c)   9.8 × 103 N
(d)   1.3 × 104 N
(e)   1.5 × 104 N

### QUESTION 23**

An object will always accelerate in the same direction as the net force acting on it.

(T)   True
(F)   False

### QUESTION 24**

Two balls are thrown from the same height at the same time. Ball 1 is thrown with initial velocity v1 = 20 m/s at an angle q1= 30° above horizontal. Ball 2 is thrown with initial velocity v2 = 10 m/s at an angle q2 = 60° above horizontal. Which one of the following statements is true?

(a)   Ball 1 hits the ground before Ball 2.
(b)   Ball 1 hits the ground at the same time as Ball 2.
(c)   Ball 1 hits the ground after Ball 2.

### QUESTION 25**

A baseball is hit from ground level at an angle of q= 35° with respect to horizontal. It returns to the ground after traveling a horizontal distance of 110 m. What was the initial speed of the ball?

(a)   47.9 m/s
(b)   46.4 m/s
(c)   33.9 m/s
(d)   23.2 m/s
(e)   16.9 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.