Which of the following simple machine is used for linear motion?
Wheel and axle
The wheel and axle consist of a round disk, known as a wheel, with a rod through the center of it, known as the axle. The wheel rotates, and the axle rotates along with the wheel. When the system starts to roll on the ground, the rotation of the wheel causes the translatory motion of the centre of the wheel and axle, thus resulting in linear motion.