CA #2 E XTRA C REDIT S TUDY G UIDE
AME
LASS
K INETMATICS R EVIEW
1. A ball is in free fall. Its acceleration is: a. downward during both ascent and descent b. downward during ascent and upward during descent c. upward during ascent and downward during descent d. upward during both ascent and descent e. downward at all times except at the very top, when it is zero
2.
The diagram represents the straight line motion of a car. Which of the following statements is true? a. The car accelerates, stops, and reverses b. The car accelerates at 6 m/s 2 for the first 2 s c. The car is moving for a total time of 12 s d. The car decelerates at 12 m/s 2 for the last 4 s
3. At the instant a ball is thrown horizontally with a large force, an identical ball is dropped from the same height. Which ball hits the ground first? a. The horizontally thrown ball b. The dropped ball c. Neither -- they both hit the ground at the same time.
4. A boy on the edge of a vertical cliff 20 m high throws a stone horizontally outwards with a speed of 20 m/s. It strikes the ground at what horizontal distance from the foot of the cliff? Use g = 10 m/s 2 b. 40 m c. 50 m d. e. none of these a. 10 m
5. The diagram represents below represents the straight line motion of a car. How far does the car travel from 0 – 9 seconds?

6. A giraffe, who stands 6.00 m tall, bites a branch off a tree to chew on the leaves, and he lets the branch fall to the ground.
How long does it take the branch to hit the ground?
7. The Essex county sheriff is trying to determine the speed of a car that slid off a small bridge on a snowy New England night and landed in a snow pile 4.00 m below the level of the road. The tire tracks in the snow show that the car landed
12.0 m measured horizontally from the bridge. How fast was the car going when it left the road?
8.
A ball rolls off a 10. m high table and hits the ground 1.5 m away from the base of the table. a) what are the horizontal and vertical velocities of the ball just as it rolls off the table? b) what are the horizontal and vertical velocities of the ball the moment it hits the ground?
9. A ball is thrown into the air with a velocity of 15 m/s. What is the maximum height it reaches?
10. How do you find … a) velocity on an x vs t graph? b) Displacement on a V vs T graph?
C) Acceleration on a V vs T graph?
D) Velocity on a A vs T graph? e) How can you tell whether there is acceleration on a X vs T graph?
F) How can you tell whether there is acceleration on a V vs T graph?

F ORCES R EVIEW
1. The block shown moves with constant velocity on a horizontal surface. Two of the forces acting on the block are shown. A frictional force exerted by the surface is the only other horizontal force acting on the block. The frictional force is: a) 0 b) 2 N, leftward c) 2 N, rightward d) slightly more than 2 N, leftward e) slightly less than 2 N, leftward
2. A car travels east at constant velocity. The net force on the car is: a) east b) west c) up d) down e) zero
3. An 1.5 N ball is thrown at an angle of 30

above the horizontal with an initial speed of 12 m/s. At its highest point, the net force on the ball is: a) 9.8 N, 30 
below horizontal d) 9.8 N, down b) zero c) 9.8 N, up e) 1.5 N, down
4. Two point masses m and M are separated by a distance d. If the separation d remains fixed and the masses are increased to the values 3m and 3M respectively, how does the gravitational force between them change? a) The force will be one-third as great. b) The force will be one-ninth as great. c) The force will be three times as great. d) The force will be nine times as great. e) It is impossible to determine without knowing the numerical values of m, M, and d.
5. Two satellites of different masses are in the same circular orbit about the earth. Which one of the following statements is true concerning the magnitude of the gravitational force that acts on each of them? a) The magnitude of the gravitational force is zero newtons for both satellites. b) The magnitude of the gravitational force is the same for both satellites, but not zero newtons. c) The magnitude of the gravitational force is zero newtons for one, but not for the other. d) The magnitude of the gravitational force depends on their masses. e) The magnitude of the gravitational force varies from point to point in their orbits.
6. A 2.0-N force acts horizontally on a 10-N block that is initially at rest on a horizontal surface. The coefficient of static friction between the block and the surface is 0.50.
I. What is the magnitude of the frictional force that acts on the block? a) 0 N b) 2 N c) 5 N d) 8 N e) 10 N
II. Suppose that the block now moves across the surface with constant speed under the action of a horizontal 3.0-N force. Which statement concerning this situation is not true? a) The block is not accelerated. b) The net force on the block is zero newtons. c) The frictional force on the block has magnitude 3.0 N. d) The coefficient of kinetic friction between the block and the surface is 0.30. e) The direction of the total force that the surface exerts on the block is vertically upward.

7. Block A, with a mass of 10 kg, rests on a 30

incline. The coefficient of kinetic friction is 0.20. The attached string is parallel to the incline and passes over a massless, frictionless pulley at the top. Block B, with a mass of 8.0 kg, is attached to the dangling end of the string. a) Draw the FBD for each block. b) Write the Fnet equations in the direction of motion. c) Solve for the acceleration of the blocks.
8. A box is pushed with constant velocity across a rough floor with a force of 10 N. The coefficient of kinetic friction between the box and the floor is 0.3. What is the force of friction?
9. A 5.0 kg box is pulled across a rough floor with a force of 25 N. The coefficient of kinetic friction between the between is 0.15. a) Draw the FBD for the box b) Write the F next equation for the box. c) Find the acceleration of the box. d) If the box starts from rest and is pushed for 7.0 seconds, what will its final velocity be?

10. Which of the graphs below represents gravitational force between two objects vs the distance between them.
Explain.
Work, Energy, Impulse, & Momentum Review
1. A variable force acts on an object. The force causes the object to move along a line parallel to the line of action of the force. The graph below shows how the force varies with distance.
3 force
/N
2
1
0 1 2 3 4 5 6 7 8 9 10 distance /m
The work done by the force is approximately
A. 2.5 J
B. 4.5 J
C. 8.5 J
D. 20.5 J
2. A ball of mass 2.0 kg falls vertically and hits the ground with speed 7.0 ms -1 as shown below.
The ball leaves the ground with a vertical speed 3.0 ms -1 .
The magnitude of the change in momentum of the ball is
A. zero.
B. 8.0 N s.
C. 10 N s.
D. 20 N s.

3. A 0.2 kg rubber ball is dropped from the window of a building. It strikes the sidewalk below at 30 m/s and rebounds up at
20 m/s. The magnitude of the impulse due to the collision with the sidewalk is: a. b.
10 N × s
6.0 N × s c. d.
2.0 N × s
19.6 N × s e. 9.8 N × s
4. An 81 kg football player moving 6.5 m/s tackles and collides with a stationary 140 kg football player. What speed will the football players have the moment after impact? a. 0 m/s b. 4.8 m/s c. 2.4 m/s d. 3.8 m/s
5. A 740 kg car traveling 19 m/s comes to a complete stop in 2.0 s. What is the force exerted on the car during this stop? a. 85 N b. 850 N c. 7000 N d. 9200 N
6. The momentum of a 225 g softball moving at 35 m/s is a. 7.9 kg m/s b. 3.5 N c. 5.0 m/s d. 2.1 kg m/s
7. The purpose of an airbag in an automobile is a. to prolong the time of impact for a given change in momentum thereby reducing the force of impact b. to deliver a greater force to the car occupant upon impact c. to shorten the time of impact d. to reduce the momentum of the vehicle
8.
What is the velocity of car "B" after the collision? (Define motion to the right as being positive.)
A. -1 m/s
B. 3 m/s
C. 5 m/s
D. 8 m/s
E. 0 m/s

11. A 10-kg box, initially at rest, moves along a frictionless horizontal surface. A horizontal force to the right is applied to the box. The magnitude of the force changes as a function of time as shown.
3
2
1
Force (Newtons)
Time (seconds)
2 4 6 8 10
Calculate the impulse on the box from 0-4 seconds.
12. A parachutist with a mass of 50.0 kg jumps out of an airplane at an altitude of 1.00

10 3 m. After the parachute deploys, the parachutist lands with a velocity of 5.00 m/s. Using the work–kinetic energy theorem, find the energy that was lost to air resistance during this jump. (g =
9.81 m/s 2 .)
13. An escalator is 30.0 meters long and slants at 30.0° relative to the horizontal. If it moves at 1.00 m/s, at what rate does it do work in lifting a
50.0 kg man from the bottom to the top of the escalator?
14. How much power is needed to lift a 75-kg student vertically upward at a constant speed of 0.33 m/s?
15. Frank, a San Francisco hot dog vender, has fallen asleep on the job. When an earthquake strikes, his 300-kg hot-dog cart rolls down Nob Hill and reaches point A at a speed of 8.00 m/s. How fast is the hot-dog cart going at point B when Frank finally wakes up and starts to run after it?

16.
A bullet with a mass of 5.00 x 10 –3 kg is loaded into a gun. The loaded gun has a mass of 0.52 kg. The bullet is fired, causing the empty gun to recoil at a speed of 2.1 m/s. What is the speed of the bullet?
17. An 850 kg rollercoaster is released from rest at point A. How fast is it going at point B?
18.
A 15-N net force is applied for 6.0 s to a 12-kg box initially at rest. What is the speed of the box at the end of the 6.0-s interval?
19.
A box is dropped from a height of 15. m. Disregarding air resistance, What is its velocity when it hits the ground?
20. A moving object has a kinetic energy of 150 J and a momentum of 80 J. What is its mass?