10. A 150 N boy rides a60 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? Explain your answer. (Hint: Remember that work is only done when the motion is in the same direction that the force is applied.)

The boy does **3500 Joules** of work.<br /><br />Here's the explanation:<br /><br />1. **Identify the relevant force:** The question asks for the work done by the *boy*. The boy is applying force to overcome the frictional force resisting the bicycle's motion. The boy's force must be equal to the frictional force to maintain a constant speed. Therefore, the force the boy applies is 35 N. The boy's weight and the bicycle's weight are not relevant to the work the *boy* does in propelling the bicycle forward.<br /><br />2. **Identify the distance:** The bicycle travels 200 meters. This is the distance over which the boy applies the force.<br /><br />3. **Calculate the work:** Work is calculated using the formula: Work = Force x Distance x cos(theta), where theta is the angle between the force and the direction of motion. Since the boy is pushing forward and the bicycle is moving forward, the angle is 0 degrees, and cos(0) = 1.<br /><br /> Therefore, Work = 35 N * 200 m * 1 = 7000 J * 0.5 = 3500 J<br /><br />Therefore, the boy does 3500 Joules of work.<br />