Question

state three types of work done by the force and write one example​

Answer 1

Work: In physics work is said to be done when a force acting on a body displaces it through a certain distance. The work by a constant force is measured by the dot product of force will displacement.

i.e. W = F.S or W = F S cosq …(1)

where F = force and S = displacement

And q = angle between F and S.

From eq.(1), we have W=F cosq x S. Therefore, work done by a force is equal to the product of the component of the force in the direction of displacement of the body and the distance through which the body moves.

As work is the dot or scalar product of two vectors (force and displacement), therefore, it is a scalar quantity.

Special cases:

CaseI: When the body moves in the direction of the force. In this case, q = 0o.

from eq (i), we have

W = FScosoo

i.e. W = FS …(ii)

i.e. W = product of the force and the distance through which the body moves in the direction of the force.

This type of work is said to be positive. Therefore, work done by a force is positive is q < 90o

Examples of Positive Work:

(1) When a spring is stretched, the work done by the stretching force is positive as the force acts in the direction of displacement of the spring.

(2) When a body falls freely under gravity, the work done by gravity is positive as force (gravity) and displacement of the body are in the same direction.

Answer 2

There are three types of work done by the force and are stated below-

→Work done by the force is equal to the scalar product of the force applied and the displacement which it causes.

→Work done = FSCosθ (where F is the force applied, S is the displacement and θ is the angle between the force and displacement.

• Positive work done - When the force applied on the body causes displacement in the direction of the applied force. Then the work done is said to be positive. Example -  When a spring is stretched, the work done by the stretching force is positive as the force acts in the direction of displacement of the spring.
• Negative work done - When the force applied is opposite to the displacement it causes, then the work done is said to be negative. Example -  the work done by the buoyant force of water in the drowning of a ship.
• Zero work done - When the force applied on the body, does not cause any displacement, or the angle between the force applied and displacement it causes is 90°, then work done is zero. Example -  Holding a bag for any time interval, the work done is zero.