Define the term work. State the conditions that need to be satisfied for work to be done. Give some situations in which work is done.
(i) Push a pebble lying on a surface. The pebble moves through some distance. Here we apply a force on the pebble and the pebble gets displaced. So, we have done work on the pebble.
(ii) We apply a force to lift a book through a height. The book rises up. We have done work in moving up the book.
(iii) A bullock is pulling a cart. The cart moves. There is a force on the cart and the cart has moved. The bullock has done work on the cart.
How is work done measured when a body moves in the direction of the applied force?
Work done by a constant force when a body moves in the direction of applied force. As shown in Fig., suppose a force F acts on a body. The body moves through a distance s in the direction of the force.
Thus, work done by a force acting on a body is equal to the magnitude of the force multiplied by the distance moved in the direction of the force.
When is the work done by a force said to be
(i) positive and (ii) negative?
A car weighing 1000 kg and travelling at 30 mis stops at a distance of 50 m decelerating uniformly. What is the force exerted on it by the brakes? What is the work done by the brakes?
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