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Ch7test_WorkEnergy

Ch7test_WorkEnergy - Work and Energy 1 A constant force of...

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Work and Energy 1 1. A constant force of 12 N in the positive x direction acts on a 4.0-kg object as it moves from the origin to the point (6 i – 8 j ) m. How much work is done by the given force during this displacement? a. +60 J b. +84 J c. +72 J d. +48 J e. +57 J 2. A 5.0-kg object is pulled along a horizontal surface at a constant speed by a 15 N force acting 20 ° above the horizontal. How much work is done by this force as the object moves 6.0 m? 3. A 2.0-kg projectile moves from its initial position to a point that is displaced 20 m horizontally and 15 m above its initial position. How much work is done by the gravitational force on the projectile? 4. How much work is done by a person lifting a 2.0-kg object from the bottom of a well at a constant speed of 2.0 m/s for 5.0 s? 5. A 2.5-kg object falls vertically downward in a viscous medium at a constant speed of 2.5 m/s. How much work is done by the viscous force on the object as it falls 80 cm? a. +2.0 J b. +20 J c. –2.0 J d. –20 J e. +40 J 6. A 2.0-kg particle has an initial velocity of (5i – 4j) m/s. Some time later, its velocity is (7i + 3j) m/s. What work was done by the resultant force during this time interval, assuming no energy is lost in the process? 7. A block is pushed across a rough horizontal surface from point A to point B by a force (magnitude P = 5.4 N) as shown in the figure. The magnitude of the force of friction acting on the block between A and B is 1.2 N and points A and B are 0.5 m apart. If the kinetic energies of the block at A and B are 4.0 J and 5.6 J, respectively, how much work is done on the block by the force P between A and B? 8. A 1.4-kg block is pushed up a frictionless 14 ° incline from point A to point B by a force (magnitude P = 6.0 N) as shown in the figure. Points A and B are 1.2 m apart. If the kinetic energies of the block at A and B are 3.0 J and 4.0 J, respectively, how much work is done on the block by the force P between A and B? 9. A constant force of 15 N in the negative y direction acts on a particle as it moves from the origin to the point (3i + 3j – 1k) m. How much work is done by the given force during this displacement? a. +45 J b. –45 J c. +30 J d. –30 J e. +75 J
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