# Movement Ratio

## Machines and movement ratio (velocity ratio)

A machine is a device that can *change the magnitude and line of action of a force*.

Examples are

- pulley systems
- gear systems
- screw-jacks

A simple machine amplifies the input force (effort) to a larger output force (load).

### Movement Ratio

The *movement ratio* (or *velocity ratio*) of a machine is defined as the ratio of the distance moved by the effort to the distance moved by the load. Movement ratio can be expressed as

M_{r}= s_{e}/ s_{l}

= velocity ratio (1)

where

M_{r}= movement ratio

s_{e}= distance moved by the effort (m, ft)

s_{l}= distance moved by the load (m, ft)

### Machine Efficiency

The efficiency of a simple machine is defined as the ratio of the *force ratio to the movement ratio* and can be expressed as

μ = F_{r}/ M_{r}(2)

where

μ = machine efficiency

F_{r}= force ratio