You see a penny lying on the ground. A penny won't buy much these days, so you think: "If I bend down to pick it up I will do work. To do that work I will have to burn some energy. It probably costs me more to buy the fuel (food) to provide that energy than I would gain by picking up the penny. It's not cost effective." You pass it by. Is the argument correct? Estimate the energy cost for picking up a penny. You may find the following information useful: A jelly donut contains about 250 Calories (1 Calorie = 1 Kcal).
Page last modified December 7, 2013: H&T01