Ball Bearings are used in Bicycles, Cars, etc. Because

Use of Ball Bearing in Cars & Bicycles

Ball bearings are used in bicycles, cars, etc., because

1. the actual area of contact between the wheel and axle is increased
2. the effective area of contact between the wheel and axle is increased
3. the effective area of contact between the wheel and axle is reduced
4. None of the above statements is correct

Answer: The effective area of contact between the wheel and axle is reduced

Ball bearings are used to reduce friction between the surfaces.

A ball bearing is a type of rolling-element bearing that uses balls to maintain the separation between the bearing races. The purpose of a ball bearing is to reduce rotational friction and support radial and axial loads.

Ball bearing are used in bicycles, axel cars etc to reduce friction between the surfaces and also because the effective area of contact between the wheel axle is reduced

Ball bearings are spherical in shape. When these move they are not dragged, they roll in any direction. With a little effort (force and energy) these can be moved. The friction force that causes these to move is ROLLING friction and is minimum as compared to static friction and dynamic friction.

Why Ball bearings are used in bicycles?

A ball bearing is a type of rolling-element bearing that uses balls to maintain the separation between the bearing races. The purpose of a ball bearing is to reduce rotational friction and support radial and axial loads.
So ball bearings allow any direction of movement, and the friction associated is least and the effort required to move them is also very less. The Loss of energy in moving the ball bearings is also the least.