Impulse and Impulsive Force An impulsive force is
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Impulse and Impulsive Force An impulsive force is a large force that acts over a short period of time during collisions or explosions. Examples of impulsive force are : a) Hitting a golf ball b) Hitting a nail using hammer c) Collision of cars d) Cannon firing
The product of impulsive force, F and the time of impact, t is known as the impulsive of the force. Consider an impulsive force, F and the following equations : F = ma …………………. (1) and a = v – u ………………. (2) t substitute (2) into (1), F = m v – u ……………. (3) t F = mv – mu , therefore Ft = mv –mu ……. . (4) t
From equation (4), impulse, Ft is equal to the change of momentum brought about the impulsive force. Impulse, Ft = mv –mu = change of momentum The SI unit for the impulse is kg m s-1 or N s. Impulse is a vector quantity. From equation (3), F = mv – mu t Therefore, impulsive force can be defined as the rate of the change of momentum in a collision or an explosion.
Effect of time on the magnitude of impulsive force F = mv – mu = change of momentum t time of impact F is inversely proportional to the time of impact The shorter the time of impact, the bigger the impulsive force while the longer the time of impact, the smaller the impulsive force. a) A car crashes into a tree and stop. Due to the hard surface of the tree, t is very short. Hence, F that acts is very big.
If the car crashes into loose sand, this will lengthen the time of impact and will reduce the F acting on the car and prevent less injury. Increasing the time of impact (t) to reduce the impulsive force (F) 1. A high jumper falls on a thick piece of mattress. The soft mattress lengthens the t and reduces the F acting on the high jumper.
2. When a goalkeeper catches a fast -moving ball, he wears glove to increase the time of contact when stopping the ball. With longer t, a smaller F is acting on his hand. 3. When you jumps from high place, you are advice to bend your legs to increase the t. Hence, the F acting on your leg is smaller and can reduce injury.
The beneficial effect of Impulsive Force Pestle and mortar are made of stone. When a pestle is used to pound onion, chili, garlic or ginger. The hard surfaces of both the pestle and mortar cause the pestle to be stopped in a very short time. A large impulsive force is resulted and thus causes these spices to be crushed easily.
Safety features in vehicles Safety glass. Safety belts. Side-impact bars. Front crumple zone. Anti-lock breaking system (ABS). Air bags and soft materials dashboard.
