Question

Why does a horse need to pull harder during the first few steps in pulling the cart?
A. Limiting friction is greater than dynamic friction.
B. sliding friction is greater than rolling friction.
C. No frictional force acts after the cart comes in motion.
D. Air friction is greater during the first few steps of the motion.

Answer 1

Hint: Friction is the force acting between the object and the surface.Coefficient of limiting friction is greater than the coefficient of kinetic frictionCoefficient of kinetic friction is greater than the coefficient of rolling friction.

Complete answer:
Because the horse has to work against the maximum value of static friction that comes into play when a body is just at the verge of sliding over the surface of another body, the horse has to pull the cart harder during the initial few steps of his motion. This is known as the limiting friction.

The horse needs to draw the cart harder during the first few steps of his motion because he has to fight against the limiting friction, but after the motion begins, he has to work against the dynamic friction, which is less than the limiting friction. As a result, the horse will have to exert more force during the initial few steps of pulling the cart.

Therefore option A is the correct answer.

Note: It is always easier to pull than to push because the force of friction increases when the normal reaction of the surface on the object increases. Mathematically, we can show this relation as $$F_r=\mu N$$. In the case of pulling, the value of normal reaction is smaller and greater in pushing.