3. The diagram shows two bowling balls, A and B, each having a mass of 7.00 kilograms, placed 2.00 meters apart.

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1 1. Which statement describes the gravitational force and the electrostatic force between two charged particles? A) The gravitational force may be either attractive or repulsive, whereas the electrostatic force must be attractive. B) The gravitational force must be attractive, whereas the electrostatic force may be either attractive or repulsive. C) Both forces may be either attractive or repulsive D) Both forces must be attractive. 2. Which diagram best represents the gravitational forces, Fg, between a satellite, S, and Earth? A) B) 3. The diagram shows two bowling balls, A and B, each having a mass of 7.00 kilograms, placed 2.00 meters apart. What is the magnitude of the gravitational force exerted by ball A on ball B? A) N B) N C) N D) N 4. The centers of two 15.0-kilogram spheres are separated by 3.00 meters. The magnitude of the gravitational force between the two spheres is approximately A) N B) N C) N D) N C) D) 5. The gravitational force of attraction between two objects would be increased by A) doubling the mass of both objects, only B) doubling the distance between the objects, only C) doubling the mass of both objects and doubling the distance between the objects D) doubling the mass of one object and doubling the distance between the objects 6. Compared to the mass of an object at the surface of the Earth, the mass of the object a distance of two Earth radii from the center of the Earth is A) the same B) twice as great C) one-half as great D) one-fourth as great

2 7. Two equal point masses are separated by a distance of 1 meter. If one mass is doubled, the gravitational force between the two masses would be A) one-half as great B) two times greater C) one-fourth as great D) four times greater 9. Which graph represents the relationship between the magnitude of the gravitational force exerted by Earth on a spacecraft and the distance between the center of the spacecraft and center of Earth? [Assume constant mass for the spacecraft.] A) 8. Two bodies attract each other with a gravitational force of 10.0 Newtons. What will be the force of attraction if the mass of each body is doubled? A) 5 N B) 10 N C) 20 N D) 40 N B) C) D) 10. When Earth and the Moon are separated by a distance of meters, the magnitude of the gravitational force of attraction between them is newtons. What would be the magnitude of this gravitational force of attraction if Earth and the Moon were separated by a distance of meters? A) N B) N C) N D) N

3 11. An object weighs 100. Newtons on Earth s surface. When it is moved to a point one Earth radius above Earth s surface, it will weigh A) 25.0 N B) 50.0 N C) 100. N D) 400. N 12. As the distance between two objects increases, the gravitational force of attraction between them will A) decrease B) increase C) remain the same 13. On the surface of Earth, a spacecraft has a mass of 2.00 x 10 4 kilograms. What is the mass of the spacecraft at a distance of one Earth radius above Earth's surface? A) kg B) kg C) kg D) kg 16. As an astronaut travels from the surface of Earth to a position that is four times as far away from the center of Earth, the astronaut s A) mass decreases B) mass remains the same C) weight increases D) weight remains the same 17. Which graph represents the relationship between the mass of an object and its distance from the Earth's surface? A) B) C) D) 14. A 65.0-kilogram astronaut weighs 638 newtons at the surface of Earth. What is the mass of the astronaut at the surface of the Moon, where the acceleration due to gravity is 1.62 meters per second squared? A) 10.7 kg B) 65.0 kg C) 105 N D) 638 N 15. What is the acceleration due to gravity at a location where a 15.0-kilogram mass weighs 45.0 newtons? A) 675 m/s 2 B) 9.81 m/s 2 C) 3.00 m/s 2 D) m/s An 8.0-newton wooden block slides across a horizontal wooden floor at constant velocity. What is the magnitude of the force of kinetic friction between the block and the floor? A) 2.4 N B) 3.4 N C) 8.0 N D) 27 N

4 19. The diagram below shows a 4.0-kilogram object accelerating at 10. meters per second 2 on a rough horizontal surface. 21. In the diagram below, the upward drag force acting on a parachute is equal in magnitude but opposite in direction to the weight of the parachutist and equipment. What is the magnitude of the frictional force Ff acting on the object? A) 5.0 N B) 10. N C) 20. N D) 40. N 20. The force required to start an object sliding across a uniform horizontal surface is larger than the force required to keep the object sliding at a constant velocity. The magnitudes of the required forces are different in these situations because the force of kinetic friction A) is greater than the force of static friction B) is less than the force of static friction C) increases as the speed of the object relative to the surface increases D) decreases as the speed of the object relative to the surface increases As a result of the forces shown, the parachutist may be moving A) downward with decreasing speed B) downward at constant speed C) upward with decreasing speed D) upward with constant acceleration 22. The diagram below represents a block sliding down an incline. Which vector best represents the frictional force acting on the block? A) A B) B C) C D) D 23. Sand is often placed on an icy road because the sand A) decreases the coefficient of friction between the tires of a car and the road B) increases the coefficient of friction between the tires of a car and the road C) decreases the gravitational force on a car D) increases the normal force of a car on the road

5 24. A book weighing 20. Newtons slides at constant velocity down a ramp inclined 30. to the horizontal as shown in the diagram below. 27. A 0.50-kilogram puck sliding on a horizontal shuffleboard court is slowed to rest by a frictional force of 1.2 newtons. What is the coefficient of kinetic friction between the puck and the surface of the shuffleboard court? A) 0.24 B) 0.42 C) 0.60 D) 4.1 What is the force of friction between the book and the ramp? A) 10. N up the ramp B) 17 N up the ramp C) 10. N down the ramp D) 17 N down the ramp 25. A box decelerates as it moves to the right along a horizontal surface, as shown in the diagram. 28. What is the magnitude of the force needed to keep a 60.-newton rubber block moving across level, dry asphalt in a straight line at a constant speed of 2.0 meters per second? A) 40. N B) 51 N C) 60. N D) 120 N 29. The diagram below shows a block sliding down a plane inclined at angle with the horizontal. Which vector best represents the force of friction on the box? A) B) C) D) 26. The diagram below represents a box shown sliding down an inclined plane. Toward which point will the force of friction on the box be directed? As angle is increased, the coefficient of kinetic friction between the bottom surface of the block and the surface of the incline will A) decrease B) increase C) remain the same 30. According to your reference table, Approximate Coefficents of Friction, what is the minimum horizontal force needed to start a 300. N steel block on a steel table in motion? A) 0.57 N B) 074 N C) 171 N D) 222 N A) 1 B) 2 C) 3 D) Jill is pulling a 200. Newton sled through the snow at constant velocity using a horizontal force of 10. Newtons. What is the kinetic coefficient of friction of the sled on the snow? A) 0.02 B) 0.05 C) 0.20 D) 20

6 32. According to your table, Approximate Coefficents of Friction, which road surface would offer the greatest traction for rubber tires? A) dry concrete B) wet concrete C) dry asphalt D) wet asphalt 33. The diagram below shows a 5.00-kilogram block at rest on a horizontal, frictionless table. Which diagram best represents the force exerted on the block by the table? A) B) C) D) 34. A man is pushing a baby stroller. Compared to the magnitude of the force exerted on the stroller by the man, the magnitude of the force exerted on the man by the stroller is A) zero B) smaller, but greater than zero C) larger D) the same 35. A high school physics student is sitting in a seat reading this question. The magnitude of the force with which the seat is pushing up on the student to support him is closest to A) 0 N B) 60 N C) 600 N D) 6,000 N

7 Base your answers to questions 36 and 37 on the information and diagram below and on your knowledge of physics. As represented in the diagram below, a constant 15-newton force, F, is applied to a 2.5-kilogram box, accelerating the box to the right at 2.0 meters per second squared across a rough horizontal surface. 36. Calculate the magnitude of the net force acting on the box. [Show all work, including the equation and substitution with units.] 37. Determine the magnitude of the force of friction on the box. Base your answers to questions 38 through 40 on the information below and on your knowledge of physics. A horizontal 20.-newton force is applied to a 5.0-kilogram box to push it across a rough, horizontal floor at a constant velocity of 3.0 meters per second to the right. 38. Determine the magnitude of the force of friction acting on the box. 39. Calculate the weight of the box. [Show all work, including the equation and substitution with units.] 40. Calculate the coefficient of kinetic friction between the box and the floor. [Show all work, including the equation and substitution with units]

8 Base your answers to questions 41 through 44 on the information below. An ice skater applies a horizontal force to a 20.-kilogram block on frictionless, level ice, causing the block to accelerate uniformly at 1.4 meters per second 2 to the right. After the skater stops pushing the block, it slides onto a region of ice that is covered with a thin layer of sand. The coefficient of kinetic friction between the block and the sand-covered ice is Calculate the magnitude of the force applied to the block by the skater [Show all work, including the equation and substitution with units.] 42. On the diagram below, starting at point A, draw a vector to represent the force applied to the block by the skater. Begin the vector at point A and use a scale of 1.0 centimeters = 5.0 newtons. 43. Determine the magnitude of the normal force acting on the block. 44. Calculate the magnitude of the force of friction acting on the block as it slides over the sand-covered ice. [Show all work, including the equation and substitution with units.]

9 Answer Key Friction test review 18 Jan B 2. C 3. C 4. C 5. A 6. A 7. B 8. D 9. D 10. D 11. A 12. A 13. B 14. B 15. C 16. B 17. A 18. A 19. B 20. B 21. B 22. B 23. B 24. A 25. D 26. B 27. A 28. A 29. C 30. D 31. B 32. A 33. A 34. D 35. C 36. Equation and substitution with units. 37. Difference between 15 N and the student's response to the previous question N 39. Fg = 49 N 40. = 0.41 or N or 196 N 44.