| Without specifying the nature or origin of the forces on the two masses, Newton's 3rd law states that if they arise from the two masses themselves, they must be equal in magnitude but opposite in direction so that no net force arises from purely internal forces.

Newton's third law is one of the fundamental symmetry principles of the universe. Since we have no examples of it being violated in nature, it is a useful tool for analyzing situations which are somewhat counter-intuitive. For example, when a small truck collides head-on with a large truck, your intuition might tell you that the force on the small truck is larger. Not so!

    "The tendency of the body  to oppose any changes in the  direction of its motion."
 
If we  observe the  video,  Bus is travelling on the road with passenger.  Passenger standing inside the bus with the help of grab handle. 
 Bus is moving fast on the road, suddenly bus should cross the curved road, Than the bus negotiates right hand curve on the road the passenger will tilt to the left side . In the same manner , if the bus negotiates left hand curve on the road the passenger will tilt to the right side, This is because of " inertia of direction".

For eg. Hitting a ball with bat fining a gun etc.

An Impulsive force doe snot remain constant but changes, firstly from zero to max and then from max. to zero.

So it is not possible to measure the exact value of force. Hence in such cases, we measure the total effect of force known as Impulse.

So Impulse of a force is defined as the measure of total effect of force. It is given by the product of force and time.