A coolie is moving on a road with a luggage on his head. Does he perform work against the force of gravity? Give reason for your answer.
No there is no work done against the force of gravity because the displacement and the direction of force are at an angle of 90°.
Walking involves doing the same amount of work against gravity as standing because the weight of the body is the same.
So, the coolie does work against gravity equal to the total weight he is carrying (his body weight and the weight of whatever he is wearing, carrying, etc).