Question

Why is it easier to pull than to push a lawn roller?

Answer 1

- Hint: When we apply the force on any object either it is moving or stationary, the amount of the force which we will apply will depend on the effectiveness of the force on that object and also weight of that particular object also counts.

Complete step-by-step answer:
Let us analyse the situation of the applied forces in both the activity (pull and push)
For push,
When we push the lawn roller then we are applying the force on the forward direction and the sine component of the friction will also be in the forward direction,
So effective weight of the lawn roller in case of pushing ${\text{ = }}{{\text{W}}_{{\text{push}}}} = mg + Fsin\theta $

For pull,
When we pull the lawn roller then we are applying the force in forward direction but the sine component of the friction will be acting in the backward direction,
So effective weight of the lawn roller in case of pulling ${\text{ = }}{{\text{W}}_{{\text{pull}}}} = mg - Fsin\theta$
Here we see that the effective weight in case of pulling is less than in pushing. Hence the force required in pulling is less.
That’s why it's easier to pull than to push the lawn roller.

Note: Here in the above solution we have considered the effective weight of the roller to compare the push and pull but if we consider the change in the friction during pushing and pulling, we will be able to explain the above in other words.
As we know that frictional force is equal to the coefficient of friction multiplied by the normal reaction force, and the normal reaction force is equal to the sum of the actual weight of the roller and the sine component of the force. In case of pull or push the actual weight of the roller is same but in case of the push the sine component is in direction of the weight while in case of the pull it is in the opposite direction of the force, hence the friction force in case of push will be more than pull, so, pull will be easier than the push.