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Unformatted text preview: 6.3. IDENTIFY: Each force can be used in the relation ( cos ) W F s F s for parts (b) through (d). For part (e), apply the net work relation as net worker grav . n f W W W W W SET UP: In order to move the crate at constant velocity, the worker must apply a force that equals the force of friction, worker k k . F f n EXECUTE: (a) The magnitude of the force the worker must apply is: 2 worker k k k 0.25 30.0 kg 9.80 m/s 74 N F f n mg (b) Since the force applied by the worker is horizontal and in the direction of the displacement, and the work is: worker worker cos 74 N cos0 4.5 m 333 J W F s (c) Friction acts in the direction opposite of motion, thus 180 and the work of friction is: k cos 74 N cos180 4.5 m 333 J f W f s (d) Both gravity and the normal force act perpendicular to the direction of displacement. Thus, neither force does Both gravity and the normal force act perpendicular to the direction of displacement....
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