Impulsive force:
A large force acting for a short time to produce a finite change in momentum is called an impulsive force.
Examples:
(i) Force exerted by a bat while hitting a ball.
(ii) Blow of a hammer on a nail.
(iii) Force experienced by a person when he falls from a certain height on a marble floor.
Impulsive forces usually vary in an abrupt and complicated manner. It is difficult to measure force and time duration separately in such situations. But the product of force and time, which is equal to the change in momentum of the body, is a measurable quantity. This product is given the name impulse.
Numerical Problems Based on Class 11 Physics Impulse
Q.1. Two billiard balls of mass 50 g moving in opposite directions with speed of 16 ms-1 collide and rebound with the same speed. What is the impulse imparted by each ball to the other?
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Answer: -1.6 kg ms-1, + 1.6 kg ms-1Q.2. A force acting on a body of mass 2 kg varies with time as shown in Fig. 5.11. Find (i) impulse of the force and (ii) the final velocity of the body.
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Answer: (i) 12 kg ms-1 (ii) 6 ms-1]Q.3. A ball moving with a momentum of 15 kg ms-1 strikes against the wall at an angle of 30° and is reflected with the same momentum at the same angle. Calculate impulse.
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Answer: 15√3 kg ms-1Q.4. A hammer weighing 1 kg moving with the speed of 10 ms-1 strikes the head of a nail driving it 10 cm into a wall. Neglecting the mass of the nail, calculate (i) the acceleration during impact (ii) the time interval of the impact and (iii) the impulse.
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Answer: (i) –500 ms-2 (ii) 0.02 s (iii) – 10 NsQ.5. A body of mass 0.25 kg moving with velocity 12 m/s is stopped by applying a force of 0.6 N. Calculate the time taken to stop the body. Also calculate the impulse of this force.
