Question

A person lifts a load in the upward direction. He applies force on the load in the upward direction due to which the object is also displaced in the upward direction.

State which of these forces does positive work on the body?

Answer 1

1. Force is defined as the external agent that causes changes in the state of motion of an object. It has both magnitude and direction.
2. Force due to gravity is the gravitational pull on an object in the downward direction.
3. Force due to gravity is obtained by, $F_g=\text{mass of an object×acceleration of the object due to gravity}$.
4. Work done is defined as the product of force and the distance moved by an object in the direction of the force.
5. As the person lifts a load in the upward direction and this applied force causes the displacement of the load in the upward direction. So, there are two forces acting on the object viz., (i) applied force $F_a$ acting in the upward direction (ii) force due to gravity $F_g$ in the downward direction. As the load is displaced in the upward direction so, the applied force must be greater than the force due to gravity that is $F_a>F_g$.
6. We know that work done is directly proportional to the force causing the displacement of an object.

Since, $F_a>F_g$, so the work done by the applied force will be positive as it causes the displacement of the load in the upward direction.