### Fall 2000 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 110. When the exam was given, the mean was 77.9; the median was 80. Click here to see the formula sheet that came with the exam.

### QUESTION 1*

This and the next two questions are about the following situation:

A car is moving in a straight line. The graph gives the velocity as a function of time.

How far does the car travel between t = 2 seconds and t = 5 seconds?

(a)   2 m
(b)   6 m
(c)   12 m
(d)   18 m
(e)   30 m

### QUESTION 2*

At which of the following times is the magnitude of the acceleration the largest?

(a)   1 s
(b)   3 s
(c)   8 s

### QUESTION 3**

The average acceleration of the car between 0 and 9 seconds is

(a)   greater than zero.
(b)   zero.
(c)   less than zero.

### QUESTION 4**

A baseball is hit straight up and is caught by the catcher 2.0 seconds later. What is the maximum height of the ball during this flight?

(a)   9.8 m
(b)   19.6 m
(c)   7.4 m
(d)   12.6 m
(e)   4.9 m

### QUESTION 5*

A ball is thrown straight downward from the top of a tall building with an initial speed of 10 m/s and hits the ground 20 seconds later. What is the speed of the ball at impact?

(a)   186 m/s
(b)   196 m/s
(c)   206 m/s
(d)   1760 m/s
(e)   2160 m/s

### QUESTION 6*

A racing car increases its speed from 10 m/s to 30 m/s with constant acceleration over a distance of 80 m. Over what period of time is the car accelerating?

(a)   8 s
(b)   5 s
(c)   2 s
(d)   10 s
(e)   4 s

### QUESTION 7**

Two balls are thrown into the air with the same initial speed. Ball A is thrown straight upward. Ball B is thrown at a 60° angle to the horizontal. Which ball is in the air for the longer time?

(a)   Ball A.
(b)   Ball B.
(c)   They both spend the same time in the air.

### QUESTION 8***

This and the next two questions are about the following situation:

You throw a ball upward with an initial speed of 10 m/s at an angle of 45° from the horizontal.

What is the speed of the ball at its maximum height?

(a)   0.0 m/s
(b)   5 m/s
(c)   6.67 m/s
(d)   7.07 m/s
(e)   10 m/s

### QUESTION 9**

How far does the ball travel horizontally before it hits the ground?

(a)   5.10 m
(b)   7.20 m
(c)   10.2 m
(d)   14.4 m
(e)   15.1 m

### QUESTION 10**

Suppose instead that the ball is thrown at 30° to the horizontal. It would go:

(a)   a greater distance
(b)   the same distance
(c)   a shorter distance

### QUESTION 11*

An airplane is traveling to a destination due north of its point of origin. It has a speed relative to the air of 400 km/h, and is traveling into a crosswind blowing 30 km/h toward the east. In what direction should the pilot point the plane so that it travels directly toward its destination?

(a)   east of north
(b)   due north
(c)   west of north

### QUESTION 12*

This and the next two questions are about the following situation:

A block of mass M = 20 kg is at rest on a horizontal surfacIt 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)   0.76
(e)   0.81

### QUESTION 13**

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

### QUESTION 14**

Suppose now a box of mass 30 kg is placed on the block. What is the magnitude of the normal force exerted by the horizontal surface on the block?

(a)   98 N
(b)   196 N
(c)   294 N
(d)   490 N
(e)   570 N

### QUESTION 15**

A block is acted upon by three forces: F1 of magnitude 60 N in the -y direction; F2 of magnitude 80 N in the –x direction; and unknown force F3 (not shown in the drawing). The block is in equilibrium. What is the magnitude of F3?

(a)   20 N
(b)   100 N
(c)   140 N

### QUESTION 16*

A block of mass M = 2 kg is on a horizontal frictionless table and is attached to one end of a string of L= 0.5 m and spun around in a horizontal circle with a constant speed v = 3 m/s. A view of the table and block from above is shown in the figure. What is the tension in the string?

(a)   36 N
(b)   75 N
(c)   95 N
(d)   156 N
(e)   212 N

### QUESTION 17**

A ball of weight W is spun around in a vertical circle at constant speeWhen the ball is at the bottom of its path, the tension in the string will be

(a)   greater than W.
(b)   equal to W.
(c)   less than W

### QUESTION 18*

A crate of mass M = 5 kg is sitting on the floor of a large truck. The coefficient of static friction between the crate and the floor is 0.75. The truck is accelerating to the right. What is the maximum acceleration of the truck such that the crate does not slide on the floor of the truck?

(a)   3.2 m/s2
(b)   5.6 m/s2
(c)   7.4 m/s2
(d)   9.8 m/s2
(e)   12.5 m/s2

### QUESTION 19***

This and the next question are about the following situation:

Two identical blocks, each of mass m, are connected to opposite ends of a string via a pulley, as shown in the figure. One block sits on a horizontal frictionless table and the other hangs vertically, with gravity pointing downward. The system is released from rest. What is the downward acceleration of the system?

(a)   2.45 m/s2
(b)   4.9 m/s2
(c)   7.35 m/s2
(d)   9.8 m/s2
(e)   12.3 m/s2

### QUESTION 20***

As the system is accelerating, what is the tension in the string?

(a)   mg/2
(b)   mg
(c)   2mg

### QUESTION 21*

A ball of weight W is suspended from the end of a string which is attached to the ceiling of an elevator. The elevator is accelerating upward. The tension in the string is

(a)   larger than W.
(b)   equal to W.
(c)   less than W.

### QUESTION 22**

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 frictional force f exerted on the block by the wall?

(a)   f = 0
(b)   f = F
(c)   f = W

### QUESTION 23*

A planet has a radius 2 times that of Earth and a mass 8 times that of Earth. How does the acceleration due to gravity on the surface of this planet (gplanet) compare with that of Earth (g) ?

(a)   gplanet > g
(b)   gplanet = g
(c)   gplanet < g

### QUESTION 24*

You are driving a car down a hill with constant velocity. The net force acting on the car is

(a)   pointing up the hill.
(b)   zero.
(c)   pointing down the hill.

### QUESTION 25*

The net force on a car moving at constant speed around a circular track is zero.

(T)   True
(F)   False

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.