How much work is done on the lawn mower by the person in Figure 7.2(a) if he exerts a constant force of 75.0 N at an angle 35° below the horizontal and pushes the mower 25.0 m on level ground? Convert the amount of work from joules to kilocalories and compare it with this person's average daily intake of 10,000 kJ (about 2400 kcal) of food energy. One calorie (1 cal) of heat is the amount required to warm 1 g of water by 1°C, and is equivalent to 4.186 J, while one food calorie (1 kcal) is equivalent to 4186 J.

Strategy
We can solve this problem by substituting the given values into the definition of work done on a system, stated in the equation The force, angle, and displacement are given, so that only the work is unknown. The force, angle, and displacement are given, so that only the work W is unknown.

Transcribed Image Text:

F cos 0 F 0 W = Fd cos 0 d