Physics 12 – Unit Exam 1

Physics 12 – Unit Exam 1

Chapters 1 through 8

For the questions that require calculations, use the space provided for the question to show how you arrived at your answer. You must show your work in order to receive credit for your answer. Use 10 m/s2 as the acceleration due to gravity at the surface of the earth.

1. A car travels east away from the ocean on Pico Boulevard at a constant velocity of 15 m/s (~30 mi/hr). How far will the car travel in 1 minute? (2)

DISTANCE = CONSTANT VELOCITY X TIME = 15 M/S X 60 S = 900 M

2. A second car is stopped at the corner of 30th and Pico. The car accelerates away from the corner at 3 m/s2.

a. After 6 seconds, how fast is the car traveling? (2)

SPEED INCREASES BY 3 M/S EVERY SEC – IN 6 SEC SPEED WILL BE 6 X 3 = 18 M/S

b. How far did the car travel in the 6 seconds? (2)

AVG VELOCITY = (0 + 18)/2 = 9 M/S.

DISTANCE = AVG VELOCITY X TIME = 9 M/S X 6 SEC = 54 M

3. The three balls shown are thrown straight upward with different initial velocities.

a. From slowest to fastest, rank the speeds of the balls 1 second after being thrown. (2)

B ( 0 M/S), C (5 M/S), A (10 M/S)

b. From slowest to fastest, rank the accelerations of the balls 1 second after being thrown. (2)

ALL ACCELERATIONS ARE THE SAME – THE ACCELERATION DUE TO GRAVITY

4. Car A accelerates from 40 to 50 mi/hr in 5 seconds. Car B accelerates from 0 to 50 mi/hr in 25 seconds. Which car has a greater acceleration? (2)

BOTH HAVE THE SAME ACCELERATION -- A (10/5 = 2), B (50/25 = 2)

5. A ball is thrown straight upward with a velocity of 20 m/s. Where is the ball located 3 seconds after being thrown? (3)

AT 3 SECONDS THE VELOCITY IS (20 – 30) = -10 M/S DOWNWARD.

AVG VELOCITY = (20 + (-10))/2 = 5 M/S.

DISTANCE = AVG VELOCITY X TIME = 5 M/S X 3 SEC = 15 M ABOVE WHERE IT WAS THROWN.

6. Three blocks are shown with horizontal forces acting on them.

a. Rank them from the greatest net force to the least net force. (2)

B (10 N), C (7 N), A (5 N)

b. Rank them from the greatest acceleration to the least acceleration. (2)

A and B (2.5 m/s2), C (1.2 m/s2)

c. Rank them from the greatest inertia to the least inertia. (2)

C (6 kg), B (4 kg), A (2 kg)

7. A 20 kg box is being pulled to the right across the floor by a horizontal force of 400 N. Is the friction force acting on the box greater than 400 N, equal to 400 N, or less than 400 N for the following situations?

a. The box is traveling at a constant speed. (2) FRICTION = 400 N

b. The box is traveling faster and faster. (2) FRICTION LESS THAN 400 N

8. A 2 kg steel ball is stationary and suspended from the ceiling by a string.

a. What does Newton’s First Law say about an object that is stationary? (2)

IF STATIONARY, THEN THE NET FORCE = 0

b. Name the two forces acting on the ball and indicate the directions in which they point. (2)

FORCE THE STRING EXERTS ON THE BALL UPWARD

FORCE THE EARTH EXERTS ON THE BALL PULLING DOWNWARD (GRAVITY)

c. Name the reaction forces to the forces in part b and indicate the directions in which they point. (2)

FORCE THE BALL EXERTS ON THE STRING PULLING DOWNWARD

FORCE THE BALL EXERTS ON THE EARTH PULLING UPWARD

9. Suppose you are pushing a 100 kg box to the right across a smooth

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