Force And Laws Of Motion

Quickly browse through questions and notes on related topics. You can also download and read this topic offline.

• Questions
• Summary

Momentum:

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, the 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 :

1. A person gets injured in the case of hitting by a moving object, such as stone, pebbles or anything because of the momentum of the object.
2. Even a small bullet is able to kill a person when it is fired from a gun because of its momentum due to great velocity.
3. A person gets injured severely when hit by a moving vehicle because of the momentum of the vehicle due to mass and velocity.

Unit of momentum :

SI unit of mass = kg

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

We know that Momentum (p) = m × v

Therefore, p = kg × m/s

Or p = kg m/s

Therefore, SI unit of momentum = kg m/s

Second Law of Motion

The rate of change of momentum of an object is proportional to applied unbalanced force in the direction of the force.

Mathematical expression

Suppose, Mass of an object = m kg

Initial velocity of an object = u m/s

Final velocity of an object = v m/s

So, Initial momentum, p₁ = mu, Final momentum, p₂ = mv

∴ Change in momentum = Final momentum – Initial momentum

= mv – mu
= m(v – u)
p = m(v - u)

∴ Rate of change of momentum = Change in momentum/Time taken

= m(v - u)/t

According to IInd law, this rate of change is momentum is directly proportional to force.