Question

What is a single movable pulley? What is its mechanical advantage in the ideal case?

Answer 1

A pulley is a machine or mechanical device that is used to lift objects. Two main forces that act on objects lifted by a pulley are force of gravitation and tension. There are different types of pulleys and single pulleys can be connected together. The mechanical advantage tells us about the performance of a machine.

Complete answer:
A mechanical device that uses pull objects is called a pulley. It consists of a wheel, an axle passing through the centre of the wheel, a chain, rope or string.

The axle is the axis of rotation of the pulley.

There are different types of pulleys; compound, movable and fixed.

A movable pulley is a pulley that is attached to a support and can move such that its axis of rotation is not fixed. It can move up and down. Some examples of a movable pulley are construction cranes, modern elevators etc.

Mechanical advantage tells us about the performance of a machine. If the mechanical advantage of a machine is non-zero then the output force is greater than the force we put in. This helps us in lifting the heavy objects more easily.

The mechanical advantage of a movable pulley in the ideal case is 2.

Therefore, a movable pulley is a pulley that does not have a fixed axis of rotation. In the ideal case, its mechanical advantage is 2.

Note:
Even though the mechanical advantage of a movable pulley is greater than a fixed pulley, the work done in both types of pulleys is the same. The mass of the pulley is assumed to be negligible in most cases of mechanics. The tension in the string on both sides of the pulley is the same.