Name: Physics R - CHAPTER 4 TEST Force and the Laws of Motion PLEASE WRITE YOUR ANSWER TO THE LEFT OF THE QUESTION. 1. Which of the following is the cause of acceleration or the change in an object’s motion? a. speed b. force c. inertia d. velocity 2. Which of the following statements does NOT describe force? a. Force causes objects at rest to remain stationary. b. Force causes objects to start moving. c. Force causes objects to stop moving. d. Force causes objects to change direction. 3. A car goes forward along a level road at constant velocity. The additional force needed to bring the car into equilibrium is a. greater than the normal force times the coefficient of static friction. b. equal to the normal force times the coefficient of static friction. c. the normal force times the coefficient of kinetic friction. d. zero. 4. Which statement about the acceleration of an object is correct? a. The acceleration of an object is directly proportional to the net external force acting on the object and inversely proportional to the mass of the object. b. The acceleration of an object is directly proportional to the net external force acting on the object and directly proportional to the mass of the object. c. The acceleration of an object is inversely proportional to the net external force acting on the object and inversely proportional to the mass of the object. d. The acceleration of an object is inversely proportional to the net external force acting on the object and directly proportional to the mass of the object. 5. A hammer drives a nail into a piece of wood. Identify an action-reaction pair, and compare the forces exerted by each object. a. The nail exerts a force on the hammer; the hammer exerts a force on the wood. b. The hammer exerts a force on the nail; the wood exerts a force on the nail. c. The hammer exerts a force on the nail; the nail exerts a force on the hammer. d. The hammer exerts a force on the nail; the hammer exerts a force on the wood. 6. The statement by Newton that for every action there is an equal but opposite reaction is which of his laws of motion? a. first b. third c. second d. fourth 7. The magnitude of the force of gravity acting on an object is a. frictional force. b. inertia. c. weight. d. mass. 8. Two perpendicular forces, one of 45.0 N directed upward and the second of 60.0 N directed to the right, act simultaneously on an object with a mass of 35.0 kg. What is the magnitude of the resultant acceleration of the object? a. 8.68 m/s2 b. 5.25 m/s2 c. 3.00 m/s2 d. 1.41 m/s2 9. An elevator weighing 2.00 × 105 N is supported by a steel cable. What is the tension in the cable when the elevator is accelerated upward at a rate of 3.00 m/s2? (g = 9.81 m/s2) a. 1.39 × 105 N b. 2.42 × 105 N c. 2.31 × 105 N d. 2.61 × 105 N 10. A free-body diagram of a ball in free fall in the presence of air resistance would show a. a downward arrow to represent the force of air resistance. b. only a downward arrow to represent the force of gravity. c. a downward arrow to represent the force of gravity and an upward arrow to represent the force of air resistance. d. an upward arrow to represent the force of gravity and a downward arrow to represent the force of air resistance. 11. If a non-zero net force is acting on an object, then the object is definitely a. at rest. b. moving with a constant velocity. c. being accelerated. d. losing mass. 12. A measure of the quantity of matter is a. density. b. force. c. weight. d. mass. 13. How much force is needed to accelerate a truck with a mass of 1500 kg from rest to 40 m/s in 10 seconds? a.150 N b. 400 N c. 4000 N d. 6000 N 14. As you push your couch across the floor at a slow but constant velocity a. friction exerts a force against the direction of movement equal to the force with which you are pushing the couch. b. there is a positive net force exerted on the couch. c. on a perfectly smooth floor the downward force of gravity would still require you to exert a force to keep the couch moving. d. none of the above. 15. In which of the following cases is the net force on an object zero? a. A sports car that is accelerating from 0 to 60 mph in 4.8 seconds. b. A motorcycle traveling at a constant velocity of 50 mph. c. A high jumper at the peak of her jump. d. none of the above. 16. Two cables are attached to an old telephone pole at right angles to each other. Each is pulled with a force of 5000 N. What is the net force on the pole exerted by the two cables? a. 7071N b. 6789N c. 8397N d. 4750N 17. A car accelerates at a constant rate of 2.9 m/s2. A continuous force of 2200N along the direction of motion is responsible for this acceleration. What is the mass of the car? a. 638 kg b. 758 kg c. 945 kg d. 1200 kg 18. What force must be applied for a 900 kg car to accelerate at 3.2 m/s2? a. 67 N b. 281 N c. 1250 N d. 2880 N 19. A tug of war game is played at a summer picnic. One team pulls to the east with a force of 300 N while the other team pulls west with a force of 400 N. If the ropes of each team are attached to a cart in the center that has a mass of 150 kg, what will be the acceleration of the cart? a. 1.5 m/s2 b. 0.66 m/s2 c. 0.75 m/s2 d. 0.5 m/s2 20. A man pushes on a wall out of frustration with a force of 30 N. What force does the wall exert on the man? a. 60 N b. 30 N c. 15 N d. 0 N 21. What is the acceleration of a 100 kg cart that has the following two forces exerted on it? One force is 50 N east; a second force is 50 N to the south. (Neglect any effect due to friction.) a. 0.71 m/s2, SE b. 1.2 m/s2, SE c. 2.5 m/s2, SE d. 2.7 m/s2, SE 22. A car cuts in front of you and you apply the brakes. Your body continues to move forward. Which best illustrates this process? a. Newton’s 1st Law b. Newton’ 2nd Law c. Newton’s 3rd Law d. Newton’s 4th Law Free Response Questions 23. Four forces are acting on a hot-air balloon: F1 = 2280.0 N up, F2 = 2250.0 N down, F3 = 85.0 N west, and F4 = 12.0 N east. a. Draw the FBD for the above situation. b. What is the magnitude and direction of the net external force on the balloon? 24. A child pulls a toy by exerting a force of 15.0 N on a string that makes an angle of 55.0° with respect to the floor. a. Draw the FBD for the above situation. b. What are the vertical and horizontal components of the force? 25. A traffic signal is supported by two cables, each of which makes an angle of 40.0° with the vertical. If each cable can exert a maximum force of 7.50 × 102 N. a. Draw the FBD for the situation. b. What is the largest weight they can support? 26. A dogsled with a mass of 47 kg is loaded with 33 kg of supplies. If the coefficient of kinetic friction between the sled’s runners and the snow is 0.075, what is the magnitude of the frictional force on the sled as it moves across flat ground? 27. A cabinet initially at rest on a horizontal surface requires a 115 N horizontal force to set it in motion. If the coefficient of static friction between the cabinet and the floor is 0.38, a. Draw the FBD for the above situation. b. What is the normal force exerted on the cabinet? c. What is the mass of the cabinet? 28. A 90.0 kg skier glides down a slope with an incline of 17.0°. a. Draw the FBD for the situation. b. What frictional force is needed for the skier to move at a constant velocity? 29. A crate is pushed across a level floor by a force of 3.00 × 102 N exerted at an angle of 20.0° below the horizontal. The coefficient of kinetic friction between the crate and floor is 0.250. a. Draw the FBD for the above situation. b. If the crate’s velocity is constant, what is the magnitude of the normal force exerted on the crate by the floor? c. What is the mass of the crate?
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