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1. How Much Work Is Done by Friction If a 20 Kg Block 7

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1. How Much Work Is Done by Friction If a 20 Kg Block 7 1. How much work is done by friction if a 20 kg block 7. A student pulls a block 3.0 meters along a horizontal sliding at 10 m/s is slowed down to 4m/s? surface at constant velocity. The diagram below shows the components of the force exerted on the A) 84 joules B) 100 joules block by the student. C) 125 joules D) 200 joules E) 840 joules 2. How much work is done by a 2,000 kg rocket moving at a constant 0.5 c far from any source of gravitational or electromagnetic force in 5 meters? A) 0 joules B) 250 c joules C) 250 c 2 joules D) 5,000 c joules E) 50,000 c joules 3. How much work is done lifting a 40 newton block 2 How much work is done against friction? meters? A) 6 J B) 18 J C) 24 J D) 30 J E) 42 J A) 20 joules B) 38 joules 8. A horizontal force of 40 N is used to push a block C) 40 joules D) 42 joules along a horizontal surface at a constant speed of 2 E) 80 joules meters per second. How much work is done on the 4. How much work is done pushing a 10 kg box up a block in 6 seconds? frictionless 30 degree incline 5 meters high at a A) 80 J B) 120 J C) 180 J D) 240 J E) 480 J constant rate? 9. How much work is done as a box of weight W is A) 500 joules B) 700 joules vertically lifted with an acceleration g, to a height h? C) 1,000 joules D) 1,500 joules E) 2,000 joules A) Wh B) Whg2 5. A 30 newton box is being pushed at a constant rate. C) Wh The coefficient of friction is 0.1 what is the work g done pushing the box 10 meters against friction? D) 2Wh A) 3 joules B) 10 joules g C) 15 joules D) 30 joules E) 2Wh E) 60 joules 10. If L, M and T denote the dimensions of length, mass, 6. In order to demonstrate some concepts of physics, a and time, respectively, what are the dimensions of physics teacher pushes against a wall with a force of energy? 300 N for 5 s. As you can imagine, the wall remains A) M/T2 B) ML/T2 stationary. How much work does the teacher do on C) ML2/T2 D) M/L2 the wall in this time period? E) T2/M A) 0 J B) 0.017 J 11. A person lifts a box with a mass of 2.0 kg from the C) 60 J D) 750 J ground to a shelf 0.5 m high. The work that gravity E) 1500 J does on the box is equal to A) –10 J B) –5 J C) 0 J D) 5 J E) 10 J 12. An object with a mass of 2 kg is attached to the end of a 3 m long string and is whirled horizontally in a circle with a constant speed of 5 m/s. When the object has traveled half a revolution, how much work has been done by the centripetal force? A) 0 J B) 50 J C) 100 J D) 150 J 16. A block of mass M is pulled by a constant force F at E) 300 J an angle of 30° relative to the ground for a distance of L meters. What is the net work done? 13. A vertical force of 500 N acts on a 12 kg mass over a horizontal displacement of 2 m. The work done by A) MLFcos30 the force is B) LFcos30 C) Lcos30 A) 0 J B) 24 J D) Fcos30 C) 1000 J D) 6000 J ML E) 12000 J E) MLcos30 F 17. Which of the following is not a vector quantity? A) Torque B) Velocity C) Work D) Momentum E) Force 18. If a 5,000 kg runaway truck is traveling 30 m/s, how 14. A woman pushes a lawn mower with a force of F at high must a ramp be to bring the truck to a complete an angle to the ground. If F = 20N and = 30°, stop? what is the net work done in moving the lawnmower A) 25 meters B) 45 meters 5m? C) 90 meters D) 1,80 meters A) 25 J B) 50 J E) 250 meters C) 86.67 J D) 14.4 J 19. A 1 kg radio controlled car is traveling at 10 m/s. E) 35 J When the car is 5 meters from a cliff the operator 15. A ball of mass 16 kg on the end of a string is spun at hits the brakes. How much force is required to stop a constant speed of 2.0 m/s in a horizontal circle the car? with a radius of 1 m. What is the work done by the A) 5 newtons B) 10 newtons centripetal force during one complete revolution? C) 20 newtons D) 50 newtons A) 0 J B) 16 J C) 32 J D) 8 J E) 4 J E) 100 newtons 20. Just before hitting a nail, a 2 kg hammer is moving at 10 m/s just before it hits a nail. If the wood exerts a constant 180 newton force on the nail, how far does the nail go? A) 0.1 meters B) 0.6 meters C) 1 meter D) 2 meters E) 4 meters 21. A 10 newton block sliding on a frictionless surface 26. A person does 100 joules of work in pulling back the goes up a ramp 3 meters high. If the block is initially string of a bow. What will be the initial speed of a traveling at 10 m/s what is the final velocity of the 0.5-kilogram arrow when it is fired from the bow? block? A) 20 m/s B) 50 m/s A) 5 m/s B) 7 m/s C) 200 m/s D) 400 m/s C) 10 m/s D) 30 m/s E) 800 m/s E) 40 m/s 27. Which of the following graphs best represents the 22. If a 200 kg cart going 30 m/s brakes with a force of kinetic energy K of a particle as a function of the 1,000 newtons how far will it travel before coming momentum p of the particle? to a stop? A) B) A) 9 meters B) 18 meters C) 90 meters D) 180 meters E) 900 meters 23. Which of the following is true of a 1 kg mass and a 5 C) D) kg mass that both fall from rest from the same height? A) the force felt due to gravity is the same on both masses B) their initial potential energies are equal 28. A 100 W motor propels an object with a mass of 4 C) they lose potential energy at the same rate kg for 2 s from rest. Its final velocity will be D) they have the same kinetic energy upon hitting A) 5 m/s B) 10 m/s the ground C) 20 m/s D) 40 m/s E) their accelerations are equal E) 100 m/s 24. What happens to the energy of a bouncing ball as it 29. An object with a mass of 2 kg increases in speed hits the ground with a certain downward velocity? from 4 m/s to 12 m/s in 3 s. The total work A) Gravitational Potential energy is converted into performed on the object during this time is kinetic energy. A) 16 J B) 64 J C) 128 J D) 256 J E) 512 J B) Elastic Potential Energy is converted into 30. A rail gun is able to accelerate a projectile with a gravitational potential energy mass of 4 kg from rest to 100 m/s in 5 s. Calculate C) Kinetic energy is converted into heat energy. the work done on the projectile by the force of the D) Kinetic energy is converted into elastic rail gun. potential energy and heat. 2 E) Kinetic energy is converted into gravitational A) 1.0 × 10 J energy. B) 5.0 × 102 J C) 2.0 × 104 J 25. If an object sliding on a rough surface experiences 5 an increase in kinetic energy of E while it is pushed D) 1.0 × 10 J by a constant force F through a distance d, what is E) Cannot be determined from the information the force to due to friction? provided. A) F d – E B) (Fd – E)/d C) (F – E)/d D) Fd E) E/d – F Base your answers to questions 35 through 37 on the picture below, which represents a plane 10 m in length with a coefficient of kinetic friction of 0.2, inclined at an angle of 53º. A block of weight 30 N is placed at the top of the plane and allowed to slide 31. Two balls of equal size are dropped from the same down. height from the roof of a building. One ball has mass M and the other has a mass 2M. When the balls reach the ground, how do the kinetic energies of the two balls compare? (Neglect friction) A) M has one-fourth the kinetic energy of 2M. B) M has one-half the kinetic energy of 2M. C) M has the same amount of kinetic energy as 2M.
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