A 150 N boy rides a 60 N bicycle a total of 200 m at a constant speed. The frictional force against the forward motion of the bicycle equals 35 N. How much work does the boy do? (Hint: Do sum of all forces first.)

W = 7000 J

Explanation:

To solve this problem we use that the speed of the bicycle is constant, therefore its acceleration is zero

            F -fr = 0

            F = fr

where F is the force applied by the child

Work is defined by

           W = F. x

           W = F x cos θ

in this case the child's force is parallel to the movement, therefore the angle is zero and cos 0 = 1

let's calculate

           W = 35 200

           W = 7000 J

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