Impulsive Force

Impulsive Force

1. Impulsive force is defined as the rate of change of momentum in a reaction. Mathematically, we write $F= mv−mu t$
2. It is a force which acts on an object for a very short interval during a collision or explosion.

Example:
A car of mass 1000kg is traveling with a velocity of 25 m/s. The car hits a street lamp and is stopped in0.05 seconds. What is the impulsive force acting on the car during the crash?

m = 1000kg
u = 24 m/s
v = 0
t = 0.05s
$F= mv−mu t F= (1000)(0)−(1000)(24) 0.05 F=480,000N$

Effects of impulse vs Force
• A force determines the acceleration (rate of velocity change) of an object. A greater force produces a higher acceleration.
• An impulse determines the velocity change of an object. A greater impulse yield a higher velocity change.
Examples Involving Impulsive Force
1. Playing football
3. Playing tennis
4. Playing golf
5. Playing baseball

Long Jump

1. The long jump pit is filled with sand to increase the reaction time when atlete land on it.
2. This is to reduce the impulsive force acts on the leg of the atlete because impulsive force is inversely proportional to the reaction time.

High Jump

(This image is licenced under the GNU Free Document Licence. The original file is from the Wikipedia.org.)
• During a high jump, a high jumper will land on a thick, soft mattress after the jump.
• This is to increase the reaction time and hence reduces the impulsive force acting on the high jumper.

Jumping

A jumper bends his/her leg during landing. This is to increase the reaction time and hence reduce the impact of impulsive force acting on the leg of the jumper.