WS-CH-4 Motion and Force Show all your work and equations used. Isaac Newton ( )

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1 AP PHYSICS 1 WS-CH-4 Motion and Force Show all your work and equations used. Isaac Newton ( ) Isaac Newton was the greatest English mathematician of his generation. He laid the foundation for differential and integral calculus. His work on optics and gravitation make him one of the greatest scientists the world has known. Multiple Choice A box that weighs 40 N is on a rough horizontal surface. An external force F is applied horizontally to the box. A normal force and a friction force are present. When force F equals 8.8 N, the box is in motion at a constant velocity. The box decelerates when force F is removed. What is the magnitude of the acceleration of the box? (Use acceleration due to gravity g = 10 m/s 2 ) (A) 0.55 m/s 2 (B) 1.1 m/s 2 (C) 4.4 m/s 2 (D) 2.2 m/s 2 A car of mass M is traveling along the roadway up a slight incline of angle θ to the horizontal when the driver suddenly applies the brakes. The car skids before coming to rest. Which expression gives the force of friction on the car if the coefficient of static friction between the tires and the road is, and the coefficient of kinetic friction is k? (A) k N (B) s N (C) mg (D) mg sin θ A 200g hockey puck slides up a metal ramp that is inclined at a 30 o angle. The coefficients of static and kinetic friction between the hockey puck and the metal ramp are = 0.4 and =0.3, respectively. The initial speed of the hockey s k puck is 14 m/s. What vertical height does the puck reach above its starting point? (Use acceleration due to gravity g = 9.8 m/s 2 ) s (A) 11 m (C) 6.6 m (B) 4.8 m (D) 14 m A 5.5 kg box slides down an inclined plane that makes an angle of 40 o with the horizontal. At what rate does the box accelerate down the slope if the coefficient of kinetic friction µk is 0.19? (Use acceleration due to gravity g = 9.8 m/s 2 ) (A) 7.5 m/s 2 (B) 6.4 m/s 2 (C) 4.9 m/s 2 (D) 5.9 m/s 2 An object is traveling uniformly at a velocity of 5 m/s. What is its final velocity if it experiences a uniform acceleration of 2 m/s 2 for 6 s? (A)12 m/s (C) 17 m/s (B) 28 m/s (D) 32 m/s

2 Kelly takes off down a 50 m high, 10 o slope on her jet-powered skis. The skis have a thrust of 260 N. The combined mass of the skis and Kelly is 50 kg. Kelly s speed at the bottom of the slope is 40 m/s. Assuming the mass of the fuel is negligible, what is the coefficient of kinetic friction of her skis on the snow? (Use acceleration due to gravity g = 9.9 m/s 2 ) (A) 0.23 (B) 0.53 (C) 0.68 (D) 0.42 An object with a mass of 60 kg moves across a level surface with a constant speed of 13.5 m/s. If there is a frictional force, and the coefficient of kinetic friction is 0.8, which must be true about the forces acting on the object? (A) There must be an unbalanced amount of vertical force acting on the object allowing it to move. (B) No forces are doing work on the object. (C) There must be some other horizontal force acting on the object. (D) The force exerted on the object by kinetic friction is negligible. Describe the forces on a system which consists of a bicycle and a rider as the rider pedals at a constant speed in a straight line? (A) Air resistance on the rider is greater than the applied force. (B) The resisting force of friction is greater than the applied forces. (C) The resisting force of friction is less than the applied forces. (D) All forces are balanced. A box of mass 80 kg is pushed in a straight line across a horizontal floor at a constant speed of 3 m/s. What is the net force on the suitcase? (Use coefficient of kinetic friction of 0.3) (A) 0 N (C) 800 N (B) 240 N (D) 27 N 10. A crate is sliding down an inclined ramp at a constant speed of 0.55 m/s. Where does the vector sum of all the forces acting on this crate point? (A) Perpendicular to the ramp (C) Vertically upward (B) Vertically downward (D) None of the above 11. Consider an inclined plane that makes an angle θ with the horizontal. What is the relationship between the length of the ramp L and the vertical height of the ramp h? (A) h L sin θ (C) L h sin θ (B) h L tan θ (D) h L cos θ What happens to a moving object in the absence of an external force? (A) Gradually accelerates until it reaches its terminal velocity, at which point it continues at a constant velocity. (B) Moves with constant velocity (C) Stops immediately (D) Slows and eventually stops An object is propelled along a straight line path by a force. If the net force were doubled, the object s acceleration would: (A) halve (C) double (B) stay the same (D) quadruple

3 A person gives a cart an initial push along a horizontal floor to get it moving and then releases the cart. The cart travels forward along the floor, gradually slowing as it moves. Consider the horizontal force on the cart while it is moving forward and slowing. Which of the following statements is correct? (A) Only a forward force is acting, which diminishes with time. (B) Only a backward force is acting, no forward force is acting. (C) Both a forward and a backward force is acting on the cart, but the forward force is larger. (D) Both a forward and a backward force are acting on the cart, but the backward force is larger. The coefficient of static friction between a box and a ramp is 0.5. The ramp s incline angle is 30 0, If the box is placed at rest on the ramp, the box will do which of the following? (A) Accelerate down the ramp (B) Accelerate briefly down the ramp but then slow down and stop (C) Move with constant velocity down the ramp (D) Not move

4 1. What breaking force is applied to a 3000 kg car that has a velocity of 40 m/s if the car is brought to a stop in 10 s? 2. What net force is needed to bring a 3000-kg car to rest from a velocity of 160 km/h within a distance of 60 m? 3. A block is launched up a frictionless incline in the diagram with an initial velocity of 5.5 m/s. What is the maximum displacement, d, of the block up the incline? 4. The block shown on the right remains at rest. What is the friction force acting on the block? 5. What is the normal force on the block in the diagram to the right 9. A block slides down a frictionless, inclined plane that makes a 30 o angle with the horizontal. What is the acceleration of this block? 10. A block slides down a 30 o incline which has a coefficient of kinetic friction 0.3. What is the acceleration of the block? 11. A 1.0 kg block of wood is attached via a pulley to a hanging 0.5 kg mass. Assuming no friction between the block and the table, calculate the acceleration of the system. 2 ( g 10.0 m / s ) 12. Two masses are connected by a light cord. The horizontal mass of 2 kg is pulled to the right with a force of 30 N along a frictionless surface. What is the tension on the cord? What is the acceleration? 6. The diagram on the right shows a 10-kg mass held at rest on a frictionless 30.0 degree incline by a force F. What is the magnitude of the force F? 13. An 8-kg mass moves up the incline where the coefficient of kinetic friction is 0.4. Assume an ideal pulley. 7. A 65-kg man is standing in an elevator that is accelerating downwards at 3.0 m/s 2. What force (normal force) does the elevator floor exert on the man s feet during this acceleration? 8. A force of 20 N acts horizontally on a mass of 10 kg being pushed up a frictionless incline that makes 30 o angle with the horizontal. What is the acceleration of the box up the incline? (a) What is the force of friction acting on the 8 kg mass? (b) What is the acceleration of each mass? (c) Find the tension on the connecting cord.

5 14. Two boxes are attached by a light cord that runs over a frictionless pulley. The mass of the block on the 60 o incline is M = 8 kg, and the mass of the block on the 45 o incline is m = 2.0 kg. (a) What is the acceleration of the blocks once released? (b) What is the total force on the cord? END OF ASSIGNMENT

6 W.S. Date / / CHAPTER 4 NAME: (Only neat and complete work will be accepted) # Given Find Formula/Work Solution