Question

Define work. State conditions when work is positive, negative and zero.

Answer 1

WORK

1. Work is the product of the component of the force in the direction of the displacement and the magnitude of this displacement.
2. It is a scalar quantity.
3. $Work=Force\times Displacement\times Cos\theta$, where $\theta$ is the angle between the force and displacement.
4. The SI unit of work is joule(J).

POSITIVE WORK

1. When force and displacement are in the same direction, the work performed on an object is said to be positive work.
2. For example: When a body moves on the horizontal surface, force and displacement act in the forward path. The work is done in this case known as Positive work.

NEGATIVE WORK

1. Negative work is performed if the displacement is opposite to the direction of the force applied.
2. For example: When an object is thrown upwards, the force of gravity is in the downward direction whereas displacement acts in the upward direction.

ZERO

1. When force and displacement are perpendicular to each other, or when force or displacement is zero.
2. For example: When we hold an object and walk, the force acts in a downward direction whereas displacement acts in the forward direction.