### Fall 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 101. The exam period was 90 minutes; the mean score was 75.9; the median score was 80. Click here to see page1 page2 of the formula sheet that came with the exam.

### QUESTION 1*

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

A football player passes the ball. The ball leaves his hand and is caught 1.7 seconds later by a receiver 30 meters away. (You may assume the ball was caught at the same height from which it was thrown.)

What is the vertical component of the velocity of the ball just after it is released?

(a)   vy = 8.3 m/s
(b)   vy = 21.3 m/s
(c)   vy = 37.0 m/s

### QUESTION 2*

What is the speed (the magnitude of the velocity) of the ball when it is at the top of its trajectory?

(a)   |v | = 0 m/s
(b)   |v | = 17.6 m/s
(c)   |v | = 24.8 m/s

### QUESTION 3**

What is the speed (the magnitude of the velocity) of the ball just before it is caught?

(a)   |v | = 18.1 m/s
(b)   |v | = 19.5 m/s
(c)   |v | = 22.9 m/s

### QUESTION 4**

This and the following question concern the same physical situation.

A 65 kg person steps onto an elevator. While riding in the elevator, the person notices their apparent weight is 767 newtons.

What do you know about the direction the elevator is moving (its velocity).

(a)   up
(b)   down
(c)   not enough information

### QUESTION 5**

What is the magnitude of the acceleration of the elevator?

(a)   |a | = 2.0 m/s2
(b)   |a | = 5.1 m/s2
(c)   |a | = 7.7 m/s2
(d)   |a | = 9.8 m/s2
(e)   |a | = 11.8 m/s2

### QUESTION 6***

A small airplane leaves from Champaign and must land at an airport 300 miles due north near Chicago. The plane travels with an air speed of 225 mph and there is a 75 mph wind coming from the west. What is the shortest time it will take for the airplane to make this trip?

(a)   t = 1.00 hours
(b)   t = 1.27 hours
(c)   t = 1.33 hours
(d)   t = 1.41 hours
(e)   t = 2.00 hours

### QUESTION 7**

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

Block A is suspended vertically by an ideal string that passes over an ideal pulley and is then connected to Block B that is resting on a frictionless ramp with incline of 35° as shown in the figure. Block B is observed to accelerate down the ramp at a rate of 3.2 m/s2. The tension in the string is 45.5 N.

What is the mass of block A?

(a)   mA = 3.5 kg
(b)   mA = 4.6 kg
(c)   mA = 5.3 kg
(d)   mA = 7.2 kg
(e)   mA = 8.2 kg

### QUESTION 8**

What is the mass of block B?

(a)   mB = 6.3 kg
(b)   mB = 7.9 kg
(c)   mB = 5.3 kg
(d)   mB = 18.8 kg
(e)   mB = 23.2 kg

### QUESTION 9**

Block B is now held fixed on the ramp (with block A still attached by the string). What is the tension in the string?

(a)   34 N
(b)   45.5 N
(c)   53.7 N

### QUESTION 10*

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

A ball is thrown vertically upward from the top of a building in Chicago with a velocity 19.6 m/s. It reaches the ground 8 seconds after it is released. This graph shows the velocity of the ball versus time t.

At what time after the ball is released (and before it hits the ground), is its velocity zero?

(a)   t = 0
(b)   t = 2 seconds
(c)   never

### QUESTION 11*

At what time after the ball is released (and before it hits the ground), is its acceleration zero?

(a)   t = 0
(b)   t = 2 seconds
(c)   never

### QUESTION 12*

The highest point the ball reaches above the building is

(a)   9.8 m
(b)   19.6 m
(c)   25.3 m

### QUESTION 13*

The height of the building is

(a)   121 m
(b)   137 m
(c)   157 m
(d)   172 m
(e)   213 m

### QUESTION 14**

This and the following question concern the same physical situation.

Three strings as shown in the figure above hold a 10 kg block. The string on the left pulls with a force of 130 N. The string in the center pulls up with a force of 125 N. Gravity points in the -y direction.

What is the vertical component of the tension in the right string, TRy?

(a)   223 N
(b)   123 N
(c)   115 N
(d)   98 N
(e)   27 N

### QUESTION 15*

What is the horizontal component of the tension in the right string, TRx?

(a)   98.N
(b)   130 N
(c)   148 N

### QUESTION 16*

In a galaxy far away, a solar system similar to our own contains several planets. One planet in this system has the same mass as Earth, but its radius is 0.62 that of Earth's radius. How much would a 67.4 kg person weigh on the surface of that planet? The mass of Earth is 5.9742 × 1024kg, the radius of Earth is 6.378 × 106 m, and the gravitational constant G = 6.674 × 10-11 N m/kg2.

(a)   175 N
(b)   661 N
(c)   1066 N
(d)   1718 N
(e)   6486 N

### QUESTION 17*

This and the following question concern the same physical situation.

A heavy truck traveling on a horizontal road with the speed of 72 km/h can stop at best within 100 m. This shortest distance occurs when the driver uses anti-lock brakes, which means that the car brakes without skidding. What is the magnitude of the acceleration of the truck?

(a)   5.0 m/s2
(b)   3.5 m/s2
(c)   2.0 m/s2

### QUESTION 18**

In the rain, on the same road, the best acceleration for this same truck is only 0.9 m/s2. What is the coefficient of static friction between the tires and the pavement in the rain?

(a)   0.09
(b)   0.50
(c)   0.90

### QUESTION 19*

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

A 5 kg block is connected to a 2 kg block by a massless string. The force F pulls the 2 kg block to the right across a flat surface. The kinetic friction coefficient between the blocks and the surface is μk = 0.2. The acceleration of the two blocks is measured to be 1.6 m/s2.

What is the magnitude of the tension T in the string?

(a)   3.2 N
(b)   8.2 N
(c)   9.8 N
(d)   17.8 N
(e)   23.3 N

### QUESTION 20**

What is the magnitude of the force F pulling the 2 kg block to the right?

(a)   7.1 N
(b)   11.2 N
(c)   17.8 N
(d)   24.9 N
(e)   42.7 N

### QUESTION 21*

What is the magnitude of the net force on the 2 kg block?

(a)   3.2 N
(b)   14.6 N
(c)   17.8 N

### QUESTION 22**

A dog pulls a cart on a horizontal surface from rest to a final velocity of 10 miles per hour. The kinetic friction coefficient between the cart and the road is μk = 0.01. While the dog speeds up, which one of the following statements is not true?

(a)   The gravitational force of the Earth on the cart is equal to the gravitational force of the cart on the Earth.
(b)   The force of the dog pulling the cart is equal to the frictional force by the road on the cart.
(c)   The gravitational force of the Earth on the cart is equal to the normal force of the road on the cart.

### QUESTION 23**

This and the following question concern the same physical situation.

Joe and his dog drove up to the bridge and walked down along the river. The graph below represents their displacement from the bridge, at x = 0, as a function of time.

Which of the following statements is not true?

(a)   v(120 s) = 1.67 m/s
(b)   v(750 s) = -3.33 m/s
(c)   Over the 1800 s interval between t = 0 and t = 1800 s, vaverage = 0 m/s.
(d)   v(1200 s) = 0.00 m/s
(e)   v(1560 s) = -5.00 m/s

### QUESTION 24*

The acceleration is always zero between 600 s and 1200 s.

(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.