Name: Class: Date: / / Momentum Quiz Review KEY Introductory Physics (670) 1. What unit is momentum measured with? kilograms meters per second 2. Decide if the objects below have momentum or not. Write yes if the underlined object has momentum and no if the object does not. a. A wagon filled with toys being pulled along the sidewalk. YES b. A plate piled high with food at rest on the table. NO c. A dump truck at rest at a stoplight. NO d. A fly moving through the air. YES 3. Which has more momentum: a baseball moving at 5 m/s or a baseball moving at 10 m/s? A baseball moving at 10 m/s has more momentum than a baseball moving at 5 m/s. 10 m/s is faster than 5 m/s. More velocity means more momentum. 4. Which has more momentum: a golf ball moving at 2 m/s or a bowling ball moving at 2 m/s? A bowling ball moving at 2 m/s has more momentum than a golf ball moving at 2 m/s. A bowling ball has more mass than a golf ball. More mass means more momentum. 5. Which has more momentum: a toy truck moving at 3 m/s or a real truck which is at rest? A toy truck moving at 3 m/s has more momentum than a real truck at rest. The real truck is at rest. An object needs to be moving to have a momentum. 6. Quantities where direction matters are called vectors. If momentum = mass velocity and velocity is speed and direction (velocity is a vector), is momentum a vector? YES #7 - #14: Circle the term in parentheses that best completes each statement. Standard(s): 2.5 TA: Independence Level: % Assistance, coaching, prompting:
7. All (stationary / moving) objects have momentum. 8. When momentum is transferred from one object to another, the total amount of momentum in the system (is / is not) conserved. 9. Momentum is calculated by multiplying (mass / weight) times velocity. 10. If two baseballs with the same mass are thrown at different velocities, the ball with a greater velocity has a (smaller / greater) momentum. 11. When a bowling ball hits a pin and knocks it down, (mass / momentum) is transferred from the ball to the pin. 12. A 6-kg puppy running at 5 m/s has a momentum of (11 kg m/s / 30 kg m/s). 13. When a truck driver slows down in a construction zone, the truck s momentum will (increase / decrease). 14. If a car and a truck are traveling at the same speed, the (car / truck) has less momentum. #15 - #18: Use the diagram to answer these questions. 15. What is the momentum of each ball? a. Ball A: = (6) (0) = 0 kg m/s b. Ball B: = (6) (15) = 90 kg m/s c. Ball C: = (10) (8) = 80 kg m/s d. Ball D: = (10) (0) = 0 kg m/s 16. Which ball has the greatest momentum? ( A B C D ) (circle your choice) 17. Of the balls that have momentum, which ball has the smallest momentum? ( A B C D ) (circle your choice) Page 2 of 7
18. Which balls do not have momentum? ( A B C D ) (circle your choices) 19. CALCULATE: Use the MCAS formula sheet to solve the following. Show ALL work. How much momentum does a 5 kg ball moving at 2 m/s have? m = 5 kg v = 2 m/s p = (5 kg)(2 m/s) p = 10 kg m/s 20. CALCULATE: Use the MCAS formula sheet to solve the following. Show ALL work. How much momentum does a 2000 kg car moving at 15 m/s have? m = 2000 kg v = 15 m/s p = (2000 kg)(15 m/s) p = 30000 kg m/s 21. MCAS QUESTION: A student is standing on a skateboard that is not moving. The total mass of the student and the skateboard is 50 kilograms. The student throws a ball with a mass of 2 kilograms forward at 5 m/s. Assuming the skateboard wheels are frictionless, how will the student and the skateboard move? a. forward at 0.4 m/s b. forward at 5 m/s c. backward at 0.2 m/s d. backward at 5 m/s Page 3 of 7
22. If you stop an object, are you changing its momentum? Yes, if you stop an object, you are changing its momentum. Momentum depends on velocity. When you are stopped, you are changing your velocity, so you are changing your momentum. 23. If you want an object to be stopped safely (smaller force), should you stop it quickly or slowly? If you want to stop an object safely, you want to do it slowly, not quickly. This is because the faster something is stopped, the less time it takes to stop it, the more force it is applied to do so. 24. Why are you safer in a car crash if an air bag stops you rather than the windshield? Use complete sentences. You are safer in a car crash if the air bag stops you because the air bar delays time it takes to stop you. Rather than stopping faster (in less time), you are stop slower (in more time). This means that there will be less force acting on you, less damage. 25. Bowling pins that are at rest do not have momentum. When a bowling ball hits the pins they will start moving, giving them momentum. If momentum is conserved where does the momentum of the moving bowling pins come from? The momentum of the pin comes from the bowling ball s momentum. The bowling ball transfers some of its momentum to the pins. The ball slows down, and the pins speed up. Page 4 of 7
26. (THIS IS AN OLD MCAS QUESTION) The illustrations below show a track with two carts before and after a collision. The mass and initial velocity of each cart are shown below. Before collision: 0.1 m/s 0.05 m/s After collision: v 2 a. What is the momentum of the first cart before it collides with the second cart? Show your calculations and include units in your answer. m = v = 0.3 m/s p = ()(0.3 m/s) p = 0.06 kg m/s b. What is the momentum of the second cart before the collision? Show your calculations and include units in your answer. m = v = 0.05 m/s p = ()(0.05 m/s) p = 0.015 kg m/s c. Describe two changes that could be made initially to either one or both carts that would result in an increase in momentum of the combined carts after collision. Page 5 of 7
You could increase the speed of the first car or increase the speed of the second car. Increasing their speeds initially will increase their speed after the collision. v = p total / (m 1 + m 2 ) = (p 1 + p 2 )/(m 1 + m 2 ) = (m 1 v 1 + m 2 v 2 )/(m 1 + m 2 ) 27. The illustrations below show a track with two carts before and after a collision. The mass and initial velocity of each cart are shown below. Before collision: 0.3 m/s 0.2 m/s After collision: v = 0 m/s a. What is the momentum of the first cart before it collides with the second cart? Show your calculations and include units in your answer. Remember to include direction. m = v = 0.3 m/s p = ()(0.3 m/s) p = 0.06 kg m/s b. What is the momentum of the second cart before the collision? Show your calculations and include units in your answer. Remember to include direction. m = v = - 0.2 m/s p = ()(- 0.2 m/s) p = - 0.06 kg m/s Page 6 of 7
c. The final velocity of the carts after the collision is zero (the carts are at rest after the collision). What is the final momentum of the combined carts? Show your calculations and include units in your answer. m = 0.5 kg v = 0 m/s p = (0.5 kg)(0 m/s) p = 0 kg m/s Page 7 of 7