## Friday, May 15, 2009

### [Physics Form 4] Impulsive Influence

Why does a stationary car have inertia but no momentum?

An object is said to have inertia when it resists any changes to the status of its motion. Inertia is proportional to mass. Since a stationary car is a matter with mass, naturally, it has inertia.

Momentum is the product of mass and velocity. A stationary car has no velocity. Hence, it has no momentum.

In order to set a stationary car in motion, a force is needed to overcome its inertia. Or you may also say that a force is needed to overcome the limitating frictional force exerted on the car.

Unlike a stationary car, a car in motion possesses both inertia and momentum. The momentum of a car is greater when it travels at a higher velocity.

Eg: A car has a greater momentum when it travels at 20m/s instead of 10m/s.

A moving car undergoes a change of momentum when it is stopped. Since the rate of momentum change is proportional to the impulsive force, a larger force is needed to stop the car traveling at a higher velocity.

Eg: A larger impulsive force is needed to stop the car moving at 20m/s instead of 10m/s.

1. Hi ,
Interesting site it's nice to see something different on blogger.
Will.

2. hello...happy teachers day!!!just four you teacher..

3. thank you...

4. this website give me some information,tq...but have to give more details like inertia and momentum..like the equation or something else

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