13.2. The coefficient of kinetic friction is the ratio of the kinetic friction force (F) between the surfaces in contact during movement to the normal force Ff/N. Both static and kinetic coefficients of friction depend on the pair of surfaces in contact.

## Does force of kinetic friction depend on weight?

Does the force of kinetic friction depend on the weight of the block? Explain. Yes. The equation for kinetic friction is F= coefficient of friction * Normal force.

Actually, the coefficient of friction does not change much with the normal force (weight of an object). The retarding force due to that friction is proportional to the normal force, F=μN, but the value of μ does not change much for a given material combination.

## Does weight change friction?

As discussed above, the more weight you put on the system, the closer the materials get, increasing the surface area, providing more friction, allowing more “weight” force into the system!

## Does more weight mean more friction?

An object of large mass is pulled down onto a surface with a greater force than an object of low mass and, as a consequence, there is greater friction between the surface of the heavy object than between the surface and the light object.

## Is always smaller than sliding friction?

As the area of contact is less in the case of rolling than in the case of sliding, rolling friction is less than the sliding friction. Rolling friction is the resistance to motion experienced by a body when it rolls upon another. It is much less than sliding friction for the same pair of bodies.

## Why is sliding friction is smaller than static friction?

The friction between the two surfaces is because of the interlocking of the irregularities of the two surfaces. During sliding, contact points do not get enough time to get interlocked properly. Therefore, less friction. This explains why sliding friction is less than static friction.

## How is rolling friction helpful?

It is also called rolling friction or rolling drag. It is one of the forces that act to oppose the motion of a driver. The main reason for this is that when the tires are in motion and touch the surface, the surface changes shape and causes deformation of the tire.