Question

The potential energy of your body is least when you are
A) sitting on a chair
B) sitting on the ground
C) sleeping on the ground
D) standing on the ground

Answer 1

Hint : We will have the least potential energy when the most amount of our body is closest to the ground. We will make use of this fact to determine the position in which the potential energy of our body is minimum.

Formula used: In this solution, we will use the following formulae
 $ U = mgh $ where $ U $ is the potential energy of the body, $ m $ is its mass, $ g $ is the gravitational acceleration, and $ h $ is the height of the center of mass of the body above the ground.

Complete step by step answer
We’ve been asked to find a situation where the potential energy of our body is minimum. To determine this position, we use the formula for potential energy which is given as
 $ U = mgh $
Our body’s center of mass lies somewhere near our stomach approximately. Since the mass of our body is constant, the potential energy will only be affected by the height of the center of mass above the ground.
When we are sitting on a chair, the center of mass of our body will lie near our stomach which is at a height equal to the height of the chair above the ground.
When we are sitting on the ground, the center of mass of our body will be a minor amount of height above the ground.
When we are sleeping on the ground, all our body parts are in contact with the ground as is our stomach. So, we will have the lowest potential energy in this position. So, the correct choice is option (C).
When we are standing on the ground, again our stomach will be at the height at which our stomach is located from the ground. So, we will have greater potential energy than in cases A) and B).

Note
The centre of mass of a human depends on the gender and the position of the limbs. Regardless of the mass distribution in a human body, since all its parts will be closest to the ground in option C), the potential energy will always be minimum in option (C).