Tuesday, December 8, 2015

Why pulling a body is easier than pushing it ?

Why pulling a body is easier than pushing the same body is the question that we would like to answer now.It is because of frictional force pulling happens to be easier than pushing a body.Weather we try to pull or push a body, we need to apply external force to move the body.Frictional force acts against the relative motion of the body.

Let us consider a body of mass m and it is on a rough horizontal surface.Let us apply a force F with an angle to the horizontal in the same way both in the case of pulling and pushing the body.

It is clear that entire force does not act in the direction of motion.We can resolve this force into components using vector resolution.We need to understand one simple rule that the component of  a vector will be in the same direction of the vector.

We can resolve the force into horizontal and vertical components.The horizontal component try to move the body and vertical component act against the gravitational force.The direction of frictional force is against the relative motion.

We know that frictional force is directly proportional to normal reaction.When two bodies are in contact,the upper body applies a force on the lower surface and the lower surface reacts by applying the same force in opposite direction.This is according to Newton's third law and according to this law,for every action,there is equal and opposite reaction.Any way they won't cancel each other as they acts on different bodies.

Normal reaction is of equal magnitude of effective action acting on the body in downward direction.This effective force is different in the case of pulling and pushing of the body.

In the case of pushing,vertical component of force acts in the down ward direction and hence the effective force is the sum of the weight of the body and the vertical component of the applied force.Thus the normal reaction in this case is of same magnitude but in the opposite direction.Hence we can calculate frictional force also as the product of coefficient of friction and normal reaction.

In the case of pulling a body with the same force and along the same direction,vertical component of force acts in the upward direction as the applied pulling force is in the outward direction.Hence its components are also outward from the centre of the body.Thus the effective force applied by the body in the difference between the weight of the body and the vertical component of force.Hence corresponding normal reaction is also less.Respectively frictional force is also less in the case of pulling when compared with pushing the same body.

As the frictional force is less in the case of pulling,it is easy to pull a body when compared with pushing the body.

It is described in the video lesson as shown in the below video.

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