4.1 ROTARY-LINEAR TRANSFORMATION WHEEL:
they let us move more easily because they reduce our contact with the ground and decrease friction. However,if there isn't enoungh friction, the wheels can slide out of control.
With each rotation, a Wheel moves forward a distance that is equal to its circumference.As a result,we need less force to move vehicles with larger wheels and they move more quickly.

Rack and pinion mechanism:The rack is a bar with many teeth and the pinion is a gear with teeth that interlock with the rack. When the pinion rotates,the rack moves in a linear direction.

Nut and bolt mechanism:A bolt or shaft with a spiral Groove and a nut that turns around it.We can turn and lighten the nut in order to hold things together.We can a use a nut and bolt mechanism to lift loads because it fuctions as a reducing system.

Winch and crank mechanism:A winch is a cylinder that rotates around a horizontal axis.Then we turn the crank to rotate the winch.The rope rolls up around the winch and lifts the load.The crank increases the force and the winch transform rotary motion into linear motion.The increase in force is proporcional to the ratio between the radius of the crank and the radius of the winch.

F*d=R*r