ch06 - Chapter 6: FORCE AND MOTION II 1. A brick slides on...

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Unformatted text preview: Chapter 6: FORCE AND MOTION II 1. A brick slides on a horizontal surface. Which of the following will increase the magnitude of the frictional force on it? A. Putting a second brick on top B. Decreasing the surface area of contact C. Increasing the surface area of contact D. Decreasing the mass of the brick E. None of the above ans: A 2. The coe cient of kinetic friction: A. is in the direction of the frictional force B. is in the direction of the normal force C. is the ratio of force to area D. can have units of newtons E. is none of the above ans: E 3. When the brakes of an automobile are applied, the road exerts the greatest retarding force: A. while the wheels are sliding B. just before the wheels start to slide C. when the automobile is going fastest D. when the acceleration is least E. at the instant when the speed begins to change ans: B 4. A forward horizontal force of 12 N is used to pull a 240-N crate at constant velocity across a horizontal f oor. The coe cient of friction is: A. 0 . 5 B. 0 . 05 C. 2 D. 0 . 2 E. 20 ans: B 5. The speed of a 4 . 0-N hockey puck, sliding across a level ice surface, decreases at the rate of . 61 m / s 2 . The coe cient of kinetic friction between the puck and ice is: A. 0 . 062 B. 0 . 41 C. 0 . 62 D. 1 . 2 E. 9 . 8 ans: A 66 Chapter 6: FORCE AND MOTION II 6. A crate rests on a horizontal surface and a woman pulls on it with a 10-N force. No matter what the orientation of the force, the crate does not move. Rank the situations shown below according to the magnitude of the frictional force of the surface on the crate, least to greatest. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .................... . . . . . . . . . . . . . 10 N 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 N 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 N 3 A. 1, 2, 3 B. 2, 1, 3 C. 2, 3, 1 D. 1, 3, 2 E. 3, 2, 1 ans: E 7. A crate with a weight of 50 N rests on a horizontal surface. A person pulls horizontally on it with a force of 10 N and it does not move. To start it moving, a second person pulls vertically upward on the crate. If the coe cient of static friction is 0 . 4, what is the smallest vertical force for which the crate moves? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ....
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This note was uploaded on 04/13/2008 for the course PHYSICS 108 taught by Professor Halstead during the Spring '08 term at SUNY Buffalo.

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ch06 - Chapter 6: FORCE AND MOTION II 1. A brick slides on...

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