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LESSON NOTES

APPLICATIONS OF NEWTON’S SECOND LAW OF MOTION

(i) A cricket player lowers his hands while catching a ball. When the ball is caught, the
impulse received by the hands is equal to the product of the force exerted by the ball
and the time taken to complete the catch. By moving the hands backwards, the cricketer
increases the time of catch. The force exerted on his hands becomes much smaller and
it does not hurt him.

(ii) A person falling from a certain height receives more injuries when he falls on a
cemented floor than when he falls on a heap of sand. In both cases, the total change in
momentum is same. On the cemented floor, the person is stopped abruptly. So, the
cemented floor exerts a large force of reaction causing him severe injuries. When the
person falls on a heap of sand, the sand yields (gets depressed) under his weight. The
person takes longer time to stop. This decreases the force exerted by the floor on the
person.

(iii) Automobiles (cars, buses, etc) are provided with shockers. When a vehicle moves
on an uneven road, it receives a jerk. The shocker increases the time of jerk and hence
reduces its force. This makes journey comfortable and saves the automobile from
damage due to bumps.
(iv) Buffers are provided between the bogies of a train. Buffers increase the time of jerk
during shunting. This decreases the force of impact between the bogies. The bogies are
thus prevented from receiving severe jerks.
(v) Chinawares are packed in straw paper before packing. The straw paper between the
chinawares increases the time of experiencing the jerk during transportation. Hence,
they strike against each other with a lesser force and are less likely to be damaged.