Question

NCERT Class.9 chapter.11 work and energy of science key point​

Answer 1

Q1. When do we say that work is done?

Work is said to be done when a force causes displacement of an object in the direction of applied force.

Q2. Write an expression for the work done when a force is acting on an object in the direction of its displacement.

Work done = Force x Displacement

Q3. Define 1J of work.

When a force of IN causes a displacement of 1m, in its own direction the work done is said to be one joule.

Q4. A pair of bullocks exerts a force of 140 N on a plough. The field being ploughed is 15 m long. How much work is done in ploughing the length of the field?

Work done = Force x Displacement = 140 x 15 = 2,100 J