You see a penny lying on the ground. A penny won\'t buy much these days, so you

Question

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).

Explanation / Answer

According to the question

We know that

Let us assume on an average , that the mass of a penny

m =2.35gms

=2.35*10-3kgs

The height to which it is to be lifted =0.915m

Therefore work done in lifting the penny

W = Fd

= 2.35*10-3 * 9.8 * 0.915m

0r W = 0.021J

Using the data 4180J = 1kcal
the energy used in doing this work =5.04*10^-6 kcal
thisenergy is very, very small even when compared to theenergy provided by a donut.

Hence the argument is not correct

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