Class 9 > MOMENTUM, Chapter Notes, Class 9, Science

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Momentum is the power of motion of an object.

The product of velocity and mass is called the momentum. Momentum is denoted by ‘p’.

Therefore, momentum of the object = Mass x Velocity.

Or, p = m x v

Where, p = momentum, m = mass of the object and v = velocity of the object.

Consider the following explanations to understand the momentum:

A person get injured in the case of hitting by a moving object, such as stone, pebbles or anything because of momentum of the object.

Even a small bullet is able to kill a person when it is fired from a gun becasue of its momentum due to great velocity.

A person get injured severely when hit by a moving vehicles, becasue of momentum of vehicle due to mass and velocity.

Since, momentum is the product of mass and velocity (p = m x v) of an object. This means momentum is directly proportional to mass and velocity. Momentum increases with increase of either mass or velocity of an object.

This means if a lighter and a heavier object is moving with same velocity, then heavier object will have more momentum than lighter one.

If a small object is moving with great velocity, it has tremendous momentum. And because of momentum, it can harm an object more severely. For example a small bullet having a little mass even kills a person when it is fired from a gun.

Usually, road accidents prove more fatal because of high speed than in slower speed. This happens because vehicles running with high speed have greater momentum compare to a vehicle running with slower speed.

Let an object with mass 'm' is in the rest.

Since, object is in rest, therefore, it's velocity, v = 0

Now, we know that,

Momentum = mass x velocity

Or, p = m x 0 = 0

Thus, the momentum of an object in the rest, i.e. non-moving,is equal to zero.

The SI unit of mass = kg

The SI unit of velocity = meter per second i.e. m/s

We know that, momentum (p) = m x v

Therefore,

p = kg x m/s

Or, p = kg m/s

Therefore, SI unit of momentum = kg m/s

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