Momentum Conservation Problems
Independent Practice
Useful Information: p = m v, and for an isolated system: po = pf.
These problems adapted from a workbook by Jennifer Bond Hickman. Note that the answers are given below. Your task is to provide ample proof of those answers, by showing known quantities, formulas and units in all appropriate places. In most cases, clear pictures of the “Before” and “After” would be a good idea as well.
Answer these problems on a separate page. A sketch would probably help in each case.
- Rhonda, who has a mass of 60.0 kg, is driving at 25.0 m/s in her sports car when she must suddenly slam on the brakes to avoid hitting a dog in the road. She is wearing her seatbelt, which brings her to a stop in 0.400 s. How much did her momentum change?
- Jamal is at the state fair playing some of the games. At one booth, he throws a 0.50 kg ball forward with a velocity of 21.0 m/s in order to hit a 0.20 kg bottle sitting on a shelf, and when the ball makes contact, the bottle goes flying forward at 30.0 m/s.
A. What is the velocity of the ball after it hits the bottle?
B. If the bottle were more massive, how would its speed after the collision compare to the 30.0 m/s it had in the example? What about the ball’s speed? Explain both your answers. - Lloyd rolls a 7.0 kg bowling ball down the alley for the league championship. One pin is still standing, and Lloyd hits it head-on with a velocity of 9.0 m/s. The 2.0 kg pin acquired a forward velocity of 14.0 m/s. What is the new velocity of the bowling ball?
- Anthony and Suzy are participating in the “Roll-a-Rama” rollerskating dance contest. While 75.0 kg Anthony rollerskates backward at 3.0 m/s, 60.0 kg Suzy jumps into his arms with a velocity of 5.0 m/s in the same direction.
A. How fast does the pair roll backwards together?
B. If Anthony is skating toward Suzy when she jumps, would their combined final velocity be larger or smaller than your answer to part A? Why? - Physics teacher Mr. McKee shoots a .22 caliber rifle at a block of wood. The rifle and the wood are mounted on light, frictionless carts. The 6.0 kg gun fires a 0.020 kg bullet with a speed of 200. m/s. The block’s mass is 0.30 kg. (The masses of the wood and the gun include the masses of the carts.)
A. What is the recoil velocity of the gun?
B. What is the velocity of the block of wood with the bullet lodged inside?
C. Suppose that, instead of lodging inside the wood, the bullet goes all the way through, and comes out with a speed of 100. m/s. What would the speed of the block be in this case?