Unit 4

163 Your Turn Solutions

1. A small car with a mass of 725 kg is moving at a velocity of 28 m/s.

a. Determine the momentum of the car.

b. A larger car (mass 2175 kg) has the same momentum as the small car. What is the velocity of the larger car?

2. A 0.145 kg baseball is pitches at a speed of 42 m/s. The batter hits the ball horizontally back toward the pitcher with an average force on the ball of 3.30 x 104 N.

a. If the ball and bat are in contact for 4.4 x 10-4 s, determine the impulse of the ball from the ball.

b. Determine the impulse of the bat.

c. Determine the change in momentum of the ball.

d. Determine the change in momentum of the bat.

3. A snowmobile has a mass of 250 kg. A constant force acts on it for 6.0 x 10 1 s. The snowmobile's initial velocity is 6.0 m/s and its final velocity is 28 m/s.

a. Determine the change in momentum.

b. Determine the magnitude of force that acts on it.

4. A sprinter with a mass of 76 kg accelerates from 0 m/s to 9.4 m/s in 2.8 seconds. Determine the average net force on the sprinter.

5. A car weighing 15,680 N and moving at 20.0 m/s is acted upon by a 640 N force until it is brought to a halt.

a. Determine its initial momentum.

b. Determine the car's change in momentum.

c. Determine the time during which the force acts upon the car.

6. A 845 kg drag racing car accelerates from rest to 28 m/s in 0.90 seconds.

a. Determine the change in momentum of the car.

b. Determine the average net force acting upon the car.

7. A force of 6 N acts upon a 3 kg object for 10 seconds.

a. Determine the object's change in momentum.

b. Determine its change in velocity.

8. Determine the force needed to stop a 1100 kg car moving at 22 m/s in 20 seconds.

9. A 10 kg brick falls from a height of 5 meters.

a. Determine the momentum of the brick just before it reaches the ground.

b. Determine the impulse needed to stop the brick.

c. If the brick stops on a thick carpet in 1.0 cm, determine the net force acting upon the brick.


d. If the brick stops on a thick 5.0 cm foam rubber, determine the net force acting upon the brick.



10. A 0.105 kg hockey puck moving at 48 m/s is caught by a 75 kg goalie who is at rest. If the goalie's skates are frictionless when on the ice, determine the speed at which the goalie and puck slide after the goalie catches it.

11. A 35 g bullet strikes a 5.0 kg block of wood and embeds itself in the block. The block and bullet fly off together at 8.6 m/s. What was the original velocity of the bullet?

12. At Great America Al Wayslookin sees Patty, the girl of his dream. He stops his bumper car (he and the car have a combined mass of 420 kg) and stares with starry eyes. Beau Friend, Patty's current date, notices Al glancing the wrong way and heads directly for the back of Al's bumper car. Beau and his bumper car have a mass of 430 kg and move toward poor Al at 10 m/s. Beau bumper car smacks into Al's bumper car and continues to move forward at 1 m/s after the collision. Determine Al's velocity after the collision.

13. Al (with a slight case of whip lash) and Beau move their bumper cars into position for a head on collision. This time Al's going to be moving. Beau's 430 kg car heads straight for Al's car moving at 10 m/s. Al's car moves straight at Beau's car in the opposite direction with a velocity of 12 m/s.

a. When the two cars collide, which car applies the greatest force upon the other?

The forces will be the same, according to Newton's third law.

b. If Al's car bounces back with a velocity of 4 m/s, determine Beau's velocity after the two cars collide.

14. A 95 kg fullback running at 8.2 m/s collides and sticks to a 128 kg defensive tackle moving in the opposite direction. After the collision, they end up with zero velocity. Determine the velocity of the tackle before hitting the fullback.

15. A car with a mass of 1250 kg moving at 28 m/s strikes a 2200 kg car at rest. If the two cars stick together, determine the speed with which they move after the collision?

16. Two students on roller skates stand face-to-face and then push each other away. One student has a mass of 90 kg, the other has a mass of 60 kg. If the 90 kg student rolls away with a velocity of -3 m/s, determine the velocity of the 60 kg student.

17. Two campers dock a canoe. One camper steps onto the dock. This camper has a mass of 80 kg and moves forward at 4 m/s. With what speed and direction do the canoe and the other camper move if their combined mass is 110 kg?

18. A 2 kg projectile and 100 kg launcher move together with a velocity of 2.0 m/s. When the 2 kg projectile is launched with a horizontal velocity of 650 m/s, what is the velocity of the launcher after the launch?

19. A 170 gram softball moving at 30 m/s is caught by a player. If the average force on the player's hand during the catch is 500 N, find the time in which the ball comes to a stop.

20. A 1000 kg car strikes a tree at 25 m/s and comes to a stop in 0.15 seconds. Find the average force acting upon the car while it is being stopped.

21. A 150 gram baseball reaches a batter with a speed of 25 m/s. After it has been struck, it leaves the bat with a speed of 35 m/s in the opposite direction. If the ball is in contact with the bat for 0.001 seconds, find the average force exerted upon it during this period.

Glenbrook South Physics Team - Tom Henderson, John Lewis, Neil Schmidgall, Dave Smith, Suzanne Webb & Brian Wegley
4000 West Lake Ave
Glenview, IL 60025 - 1200
Page Maintained by: Brian Wegley

Last Updated: October 8, 1997