Question

A ball moves along a smooth metal surface while an identical ball moves along concrete.

Which surface exerts a smaller amount of frictional force on the ball?

1. Neither concrete nor metal exert any friction on the ball because these two surfaces never result in a frictional force on any object.

2. The metal surface exerts less frictional force because there are fewer bumps and irregularities on it than there are on the concrete.

3. The concrete and metal surfaces exert the same amount of frictional force on the ball because they are both solid surfaces.

4. The concrete surface exerts less frictional force on the ball because there are fewer bumps and irregularities on the concrete than there are on the metal.

Answer 1

Answer:

2. The metal surface exerts less frictional force because there are fewer bumps and irregularities on it than there are on the concrete.

Explanation:

Frictional force is a force that is exerted between two surfaces in contact with each other. Frictional force always opposes the direction of relative motion of the two surfaces: for instance, for a ball moving along a surface, the force of friction exerted by the surface on the ball points opposite to the direction of motion of the ball.

The magnitude of the frictional force for a ball moving on a flat surface is given by

$F=\mu mg$

where

$\mu$ is the coefficient of friction

m is the mass of the ball

g is the acceleration of gravity

The value of $\mu$ depends on the type of surface involved. In particular, a smooth surface has a smaller value of $\mu$, while a rough surface will have a bigger value. In this case, we are comparing a smooth metal surface with concrete: since the metal surface has fewer bumps and irregularities than concrete, it has a smaller value of coefficient of friction, so it exerts less frictional force than concrete.