Conservation of Energy Review

Transcription

1 onservation of Energy Review Name: ate: 1. An electrostatic force exists between two coulomb point charges separated by a distance of meter. As the distance between the two point charges is decreased, the electrostatic force of attraction between the two charges decreases attraction between the two charges increases. repulsion between the two charges decreases. repulsion between the two charges increases 2. Which statement describes the gravitational force and the electrostatic force between two charged particles? The gravitational force may be either attractive or repulsive, whereas the electrostatic force must be attractive. The gravitational force must be attractive, whereas the electrostatic force may be either attractive or repulsive.. Both forces may be either attractive or repulsive.. Both forces must be attractive. 3. A metal sphere, X, has an initial net charge of coulomb and an identical sphere, Y, has an initial net charge of coulomb. The spheres touch each other and then separate. What is the net charge on sphere X after the spheres have separated? page 1

2 4. Base your answer to the following question on the diagram below, which represents two charged, identical metal spheres, and on your knowledge of physics. The number of excess elementary charges on sphere A is What is the magnitude of the electric force between the two spheres? N N N N 6. Which graph best represents the relationship between the potential energy stored in a spring and the change in the spring s length from its equilibrium position? 7. A compressed spring in a toy is used to launch a 5.00-gram ball. If the ball leaves the toy with an initial horizontal speed of 5.00 meters per second, the minimum amount of potential energy stored in the compressed spring was J J J J 8. In the diagram below, an ideal pendulum released from position A swings freely to position. As the pendulum swings from A to B, its total mechanical energy. decreases, then increases increases, only. increases, then decreases. remains the same page 2 onservation of Energy Review

3 9. A pendulum is made from a 7.50-kilogram mass attached to a rope connected to the ceiling of a gymnasium. The mass is pushed to the side until it is at position A, 1.5 meters higher than its equilibrium position. After it is released from rest at position A, the pendulum moves freely back and forth between positions A and B, as shown in the diagram below. 11. A 75-kilogram boy initially at rest skis down the slope as shown. Assuming no frictional loss, what will be his kinetic energy at the bottom of the slope? 1,500 joules 7,500 joules. 15,000 joules. 75,000 joules 12. The diagram shows a cart at four positions as it moves along its track. At which positions is the sum of the potential energy and kinetic energy of the cart the same? What is the total amount of kinetic energy that the mass has as it swings freely through its equilibrium position? [Neglect friction.] 11 J 94 J. 110 J. 920 J 10. A pendulum swings as shown in the diagram. At which position is the kinetic energy of the pendulum bob least? A and B, only B and, only. and, only. all positions, A through A B As a pendulum moves from the bottom of its swing to the top of its swing, the kinetic energy of the pendulum increases kinetic energy of the pendulum remains the same. potential energy of the pendulum decreases. potential energy of the pendulum increases page 3 onservation of Energy Review

4 14. As the pendulum swings freely from A to B as shown in the diagram, the gravitational potential energy of the pendulum 17. The diagram shown represents a frictionless track. A 10-kilogram block starts from rest at point A and slides along the track. decreases increases. remains the same 15. The work done in raising an object must result in an increase in the object s internal energy kinetic energy. gravitational potential energy. heat energy 16. As the pendulum swings from position A to position B as shown in the diagram, what is the relationship of kinetic energy to potential energy? [Neglect friction.] As the block moves from point A to point B, the total amount of gravitational potential energy changed to kinetic energy is approximately 5 J 20 J. 50 J. 500 J 18. What is the approximate potential energy of the block at point? 20 J 200 J. 300 J. 500 J 19. Base your answer(s) to the following question(s) on the information and diagram below, which is drawn to a scale of 1.0 centimeter = 3.0 meters. A 650-kilogram roller coaster car starts from rest at the top of the first hill of its track and glides freely. [Neglect friction.] The kinetic energy decrease is more than the potential energy increase. The kinetic energy increase is more than the potential energy decrease.. The kinetic energy decrease is equal to the potential energy increase.. The kinetic energy increase is equal to the potential energy decrease. Using one or more complete sentences, compare the kinetic energy of the car at the top of the second hill to its kinetic energy at the top of the third hill. page 4 onservation of Energy Review

5 20. The accompanying diagram shows a moving, 5.00-kilogram cart at the foot of a hill 10.0 meters high. For the cart to reach the top of the hill, what is the minimum kinetic energy of the cart in the position shown? [Neglect energy loss due to friction.] 23. Base your answer(s) to the following question(s) on the information and diagram below. A 250.-kilogram car is initially at rest at point A on a roller coaster track. The car carries a 75-kilogram passenger and is 20. meters above the ground at point [Neglect friction.] 4.91 J 50.0 J J. 491 J 21. The diagram below shows a 0.1-kilogram apple attached to a branch of a tree 2 meters above a spring on the ground below. ompare the total mechanical energy of the car and passenger at points A, B, and. 24. A 55.0-kilogram diver falls freely from a diving platform that is 3.00 meters above the surface of the water in a pool. When she is 1.00 meter above the water, what are her gravitational potential energy and kinetic energy with respect to the water s surface? The apple falls and hits the spring, compressing it 0.1 meter from its rest position. If all of the gravitational potential energy of the apple on the tree is transferred to the spring when it is compressed, what is the spring constant of this spring? PE = 1620 J and KE = 0 J PE = 1080 J and KE = 540 J. PE = 810 J and KE = 810 J. PE = 540 J and KE = 1080 J 10 N/m 40 N/m. 100 N/m. 400 N/m 25. The diagram below shows a toy cart possessing 16 joules of kinetic energy traveling on a frictionless, horizontal surface toward a horizontal spring. 22. A 1-kilogram rock is dropped from a cliff 90 meters high. After falling 20 meters, the kinetic energy of the rock is approximately 20 J 200 J. 700 J. 900 J If the cart comes to rest after compressing the spring a distance of 1.0 meter, what is the spring constant of the spring? 32 N/m 16 N/m. 8.0 N/m. 4.0 N/m page 5 onservation of Energy Review

6 26. A wooden crate is pushed at constant speed across a level wooden floor. Which graph best represents the relationship between the total mechanical energy of the crate and the duration of time the crate is pushed? 27. Base your answer(s) to the following question(s) on the information below. A boy pushes his wagon at constant speed along a level sidewalk. The graph below represents the relationship between the horizontal force exerted by the boy and the distance the wagon moves.. As the boy pushes the wagon, what happens to the wagon s energy? Gravitational potential energy increases. Gravitational potential energy decreases.. Internal energy increases.. Internal energy decreases.. page 6 onservation of Energy Review

7 28. A ball is dropped from the top of a cliff. Which graph best represents the relationship between the ball s total energy and elapsed time as the ball falls to the ground? [Neglect friction.] 30. Which statement describes the kinetic energy and total mechanical energy of a block as it is pulled at constant speed up an incline? Kinetic energy decreases and total mechanical energy increases. Kinetic energy decreases and total mechanical energy remains the same.. Kinetic energy remains the same and total mechanical energy increases.. Kinetic energy remains the same and total mechanical energy remains the same A child, starting from rest at the top of a playground slide, reaches a speed of 7.0 meters per second at the bottom of the slide. What is the vertical height of the slide? [Neglect friction.] 0.71 m 1.4 m. 2.5 m. 3.5 m page 7 onservation of Energy Review

8 31. The accompanying diagram shows three neutral metal spheres, x, y, and z, in contact and on insulating stands. 32. Which graph best represents the electrostatic force between an alpha particle with a charge of +2 elementary charges and a positively charged nucleus as a function of their distance of separation? Which diagram best represents the charge distribution on the spheres when a positively charged rod is brought near sphere x, but does not touch it? When a neutral metal sphere is charged by contact with a positively charged glass rod, the sphere loses electrons gains electrons. loses protons. gains protons page 8 onservation of Energy Review

9 34. In the diagram, two positively charged spheres, A and B, of masses m A and m B are located a distance d apart. 36. The diagram below shows two small metal spheres, A and Each sphere possesses a net charge of coulomb. The spheres are separated by a distance of 1.0 meter. Which diagram best represents the directions of the gravitational force, F g, and the electrostatic force, F e, acting on sphere A due to the mass and charge of sphere B? [Vectors are not drawn to scale.] Which combination of charged spheres and separation distance produces an electrostatic force of the same magnitude as the electrostatic force between spheres A and B? Which graph best represents the relationship between the kinetic energy, KE, and the velocity of an object accelerating in a straight line?.. page 9 onservation of Energy Review

10 Problem-Attic format version c EducAide Software Licensed for use by phelipedfernandes@gmail.com Terms of Use at onservation of Energy Review 2/12/ B 22. B A B Total mechanical energy is the same at all three points. A A A A 18. B 19. The car s KE is less. 20.