Forces. 3. The graph given shows the weight of three objects on planet X as a function of their mass. A. 0 N. B. between 0 N and 12 N C.

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1 Name: Date: 1. When a 12-newton horizontal force is applied to a box on a horizontal tabletop, the box remains at rest. The force of static friction acting on the box is 3. The graph given shows the weight of three objects on planet X as a function of their mass. A. 0 N B. between 0 N and 12 N C. 12 N D. greater than 12 N The acceleration due to gravity on planet X is approximately A m/s 2 B. 6.0 m/s 2 C. 9.8 m/s 2 D. 50 m/s 2 2. An 8.0-newton block is accelerating down a frictionless ramp inclined at 15 to the horizontal, as shown in the diagram below. 4. F 1 and F 2 act concurrently on point P, as shown in the accompanying diagram. What is the magnitude of the net force causing the block s acceleration? A. 0 N B. 2.1 N C. 7.7 N D. 8.0 N The equilibrant of F 1 and F 2 is A. 14 N southwest B. 14 N southeast C. 20. N southwest D. 20. N southeast page 1

2 5. Net force F causes mass m 1 to accelerate at rate a. A net force 3F causes mass m 2 to accelerate at rate 2a. What is the ratio of mass m 1 to mass m 2? 8. A book weighing 20. newtons slides at constant velocity down a ramp inclined 30. to the horizontal as shown in the accompanying diagram. A. 1 : 3 B. 2 : 3 C. 1 : 2 D. 1 : 6 What is the force of friction between the book and the ramp? A. 10. N up the ramp B. 17 N up the ramp 6. Base your answer(s) to the following question(s) on the information below. A force of 10. newtons toward the right is exerted on a wooden crate initially moving to the right on a horizontal wooden floor. The crate weighs 25 newtons. C. 10. N down the ramp D. 17 N down the ramp What is the magnitude of the net force acting on the crate? 9. If an unbalanced force of 12 newtons acts on a 6-kilogram mass, the acceleration of the mass is A. 0.5 m/sec 2 B. 2 m/sec 2 7. Is the crate accelerating? Explain your answer. C. 10 m/sec 2 D. 72 m/sec 2 page 2

3 10. The diagram shows a student applying a 10-newton force to slide a piece of wood at constant speed across a horizontal surface. After the wood is cut in half, one piece is placed on top of the other, as shown. 12. A spring has a spring constant of 25 newtons per meter. The minimum force required to stretch the spring 0.25 meter from its equilibrium position is approximately A N B N C. 6.3 N D N What is the magnitude of the force, F, required to slide the stacked wood at constant speed across the surface? A. 40 N B. 20 N C. 10 N D. 5.0 N 11. The accompanying diagram shows a child pulling a 50.-kilogram friend on a sled by applying a 300.-newton force on the sled rope at an angle of 40. with the horizontal. 13. Equilibrium exists in a system where three forces are acting concurrently on an object. If the system includes a 5.0-newton force due north and a 2.0-newton force due south, the third force must be A. 7.0 N south B. 7.0 N north C. 3.0 N south D. 3.0 N north The vertical component of the 300.-newton force is approximately A. 510 N B. 230 N C. 190 N D. 32 N page 3

4 14. Two aluminum spheres of identical mass and identical charge q hang from strings of equal length. If the spheres are in equilibrium, which diagram best represents the direction of each force acting on the spheres? Key F s = Force (tension) in string F e = Electrostatic force F g = Gravitational force A. B. C. D. page 4

5 15. The accompanying diagram shows a block on a horizontal frictionless surface. A 100.-newton force acts on the block at an angle of 30. above the horizontal. 17. Each diagram shows a different block being punched by a force across a surface at a constant velocity. In which two diagrams is the force of friction the same? What is the magnitude of force F if it establishes equilibrium? A. B. A N B N C N D. 187 N C. D. A. A and B B. B and D C. A and D D. C and D 16. A mosquito flying over a highway strikes the windshield of a moving truck. Compared to the magnitude of the force of the truck on the mosquito during the collision, the magnitude of the force of the mosquito on the truck is A. smaller B. larger C. the same page 5

6 18. The accompanying diagram shows a worker using a rope to pull a cart. 20. Which pair of forces acting concurrently on an object will produce the resultant of greatest magnitude? A. B. C. D. The worker s pull on the handle of the cart can best be described as a force having A. magnitude, only B. direction, only C. both magnitude and direction D. neither magnitude nor direction 19. A spring scale reads 20. newtons as it pulls a 5.0-kilogram mass across a table. What is the magnitude of the force exerted by the mass on the spring scale? 21. A 60-kilogram skydiver is falling at a constant speed near the surface of Earth. The magnitude of the force of air friction acting on the skydiver is approximately A. 0 N B. 6 N C. 60 N D. 600 N A. 49 N B. 20. N C. 5.0 N D. 4.0 N page 6

7 22. The accompanying diagram shows a block sliding down a plane inclined at angle θ with the horizontal. 25. On the diagram below, draw and label all vertical forces acting on the crate. As angle θ 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 26. On the diagram below, draw and label all horizontal forces acting on the crate. C. remain the same 23. What is an essential characteristic of an object in equilibrium? A. zero velocity B. zero acceleration C. zero potential energy 27. Base your answer(s) to the following question(s) on the information and diagram below. A force of 60. newtons is applied to a rope to pull a sled across a horizontal surface at a constant velocity. The rope is at an angle of 30. degrees above the horizontal. D. zero kinetic energy 24. Base your answer(s) to the following question(s) on the information below. A force of 10. newtons toward the right is exerted on a wooden crate initially moving to the right on a horizontal wooden floor. The crate weighs 25 newtons. Calculate the magnitude of the force of friction between the crate and the floor. [Show all work, including the equation and substitution with units.] Calculate the magnitude of the component of the 60.-newton force that is parallel to the horizontal surface. [Show all work, including the equation and substitution with units.] 28. Determine the magnitude of the frictional force acting on the sled. page 7