Work done by force acting on an object is equal to the magnitude of the force multiplied by the distance moved in the direction of the force. Work has only magnitude and no direction. Work done is negative when the force acts opposite to the direction of displacement. Work done is positive when the force is in the direction of displacement. The unit of work is newton-metre (N m)or joule (J).
(i) Work done is:
(a) Scalar quantity (b) Vector quantity (c) Tensor quantity (d) None of these
(ii) When force acts against the direction of displacement then work done will be:
(a) positive (b) negative
(c) both a and b can possible (d) None of these
(iii) SI unit of work is:
(a) Joule(J) (b) Newton meter(N-m) (c) both (a) and (b) (d) None of these
(iv) You are lifting stone from floor. Work is done by the force exerted by you on the stone. The object moves upwards. The force you exerted is in the direction of displacement. However, there is the force of gravity acting on the object. Which one of these forces is doing positive work?
Which one is doing negative work?
(v) Define 1 J of work.
(i) (a) Scalar quantity
(ii) (b) negative
(iii) (c) both a and b
(iv) Here work done by you is positive work as work is being done in the direction of displacement unlike in case of gravitational force which acts in downward direction against the direction of displacement which is in upward direction.
(v) When 1 Newton of force acts on body and body displaces from its position by 1 meter then the work done is said to be 1 joule (J).