Question

A man is walking with a suitcase held in his hand why is work said to be done if the man is climbing a staircase​

Answer 1

Explanation:

Man walking with a suitcase held in his hand and climbing staircase.

As man is holding the suitcase the gravity is acting on suitcase that is equal to mg (weight) and to keep holding, hand is also applying equal and opposite force upwards.

hence, angle between force(gravitational force) and displacement (upwards) is 180 degree.

Then, work is said to be done because force acting on it displaces upwards.

but, work will be negative.

thus, work= -mgh