Give four examples of wheel and axle.

1. A wheel and axle is a simple machine that consists of a wheel attached to a smaller axle so that these two parts rotate together in which a force is transferred from one to another.
2. Various examples of the wheel and axle are as follows:
   1. The doorknob
   2. The screwdriver
   3. A water wheel
   4. Steering wheel of an automobile.