Name: Date: Period: Momentum, Work, Power, Energy Study Guide

Transcription

1 Momentum, Work, Power, Energy Study Guide Your test will have fill-in-the-blank and short answer questions. Use the following to help you. Be able to answer questions about the labs (egg drop, collisions, stairs, elevator). Be able to solve number problems about work, power, and energy. See pg. 127 one-step calculations and the worksheet we did for homework for examples. Write in the following definitions: Momentum Impulse Elastic Collision Inelastic Collision Conservation of Momentum Conservation of energy Work

2 Power Energy Kinetic Energy Gravitational Potential Energy Identify what quantities the following units measure: Joules Watts Calories Horsepower

3 Be able to answer the following questions: What force is a scale measuring when you stand on it in an elevator? Why does it change? In terms of impulse and momentum, why do padded dashboards make automobiles safer? In terms of impulse and momentum, why is it important that helicopter blades deflect air downward? Why is a punch more forceful with a bare fist than with a boxing glove? Your friend says that the law of conservation of momentum is violated when a ball rolls downhill and gains momentum. What do you say? If a tennis ball and a bowling ball collide in midair, does each undergo the same change in momentum? Defend your answer. What happens to work if force is increased? What if force is decreased? What happens to work if distance is increased? What if distance is decreased?

4 What happens to power if work is increased? What if work is decreased? What happens to power if time is increased? What if time is decreased? What happens to kinetic energy if velocity is increased? What if velocity is decreased? What happens to kinetic energy if mass is increased? What if mass is decreased? What happens to gravitational potential energy if height is increased? What if height is decreased? What happens to gravitational potential energy if mass is increased? What if mass is decreased? How much work do you do on a 25-kg backpack when you walk a horizontal distance of 100 m? When you lift it a vertical distance of 100 m? At what point in its motion is the KE of a pendulum bob at a maximum? At what point is its GPE at a maximum?

5 Someone trying to sell you a SuperBall claims that it will bounce to a greater height than the height from which it was dropped. Can this be? Explain. Once used, can energy be regenerated? Is your answer consistent with the term renewable energy? How can you increase your work done when you are going up the stairs? How can you increase your power when you are lifting weights? Math practice: 1. Two ice skaters push off against one another starting from a stationary position. The 45-kg skater acquires a velocity of m/s to the right. What velocity does the 60-kg skater acquire? 2. A 0.60-kg glider traveling at 8.0 m/s on a level air track undergoes a head-on collision with a 0.20-kg mass traveling toward it at 4.0 m/s. The two gliders stick in the collision. What is the velocity of the combined gliders after the collision? 3. A glider with mass m and speed v moving along an air track collides with a stationary cart with a mass m/3. After the collision the first cart has a speed v/2. What is the velocity of the second cart? 4. A 200-kg boulder is 1000-m above the ground. a) What is its potential energy when it is 1000-m above the ground?

6 b) What is its kinetic energy when it is 1000-m above the ground? c) The boulder begins to fall. What is its potential energy when it is 500-m above the ground? Where did the lost potential energy go? d) What is the kinetic energy of the boulder when it has fallen 500-m? e) What is the kinetic energy of the boulder just before it hits the ground? 5. Calculate the work done when a force of 1 N moves a book 2 m. 6. Calculate the watts of power expended when a force of 1 N moves a book 2 m in a time interval of 1 second. 7. How many Joules of gravitational potential energy does a 1 kg book gain when it is elevated 4 m? 8. Calculate the number of Joules of kinetic energy a 1 kg book has when tossed across the room at a speed of 2 m/s.