A block of mass 4.0 kg is pushed to the right by a force of 20.0 N. A frictional force of 14.0 N is acting on the block while it is moved a distance of 12.0 m along a horizontal floor.
a) Find the work done by each of the four forces acting on the mass
b) Hence, find the net work done
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Explanation:
Force by external agent = 20 N
Frictional force = 14 N
Normal reaction = mg = 40 N
Weight = = mg = 40 N
Displacement = 12 m
a) Work done by external agent = 20 × 12 = 240J
Work done by frictional force = - 14 × 12 = - 168J
Work done by normal reaction = 40 × 0 = 0J
Work done by weight = 40 × 0 = 0J
b) Net work done = 240 - 168 = 72J
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