# Force Ratio

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

Examples of machines are

- pulley systems
- gear systems
- screw-jacks

A simple machine amplifies the input (effort) force to a larger output (load) force. The force ratio can be expressed as

F_{r}= F / S (1)

where

F_{r}= force ratio - mechanical advantage

F = load force (N, lb_{f})

S = effort force (N, lb_{f})

### Example - Force Ratio for Pulley

The effort force for a pulley with *4 ropes*, no friction loss *(μ = 1)* and load *100 kg* is calculated to* 245 N.*

The force ratio can be estimated to

*F _{r} = (100 kg) (9.81 m/s^{2}) / (245 N)*

* = 4 *

## Related Topics

### • Mechanics

The relationships between forces, acceleration, displacement, vectors, motion, momentum, energy of objects and more.

## Related Documents

### Acceleration of Gravity and Newton's Second Law

Acceleration of gravity and Newton's Second Law - SI and Imperial units.

### Bodies Moving on Inclined Planes - Acting Forces

Required forces to move bodies up inclined planes.

### Centripetal and Centrifugal Acceleration Force

Forces due to circular motion and centripetal / centrifugal acceleration.

### Equilibrant Force

The force required to keep a system of forces in equilibrium.

### Force

Newton's third law - force vs. mass and acceleration.

### Gear Reducing Formulas

Output torque, speed and horsepower with gears.

### Gears

Gears effort force vs. load force.

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Calculate hydraulic cylinder force.

### Impulse and Impulse Force

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### Levers

Use levers to magnify forces.

### Motors - Speed vs. Pulley Diameter

Pulley (Sheave) selection charts for motors ranging 850 - 3450 rpm.

### Movement Ratio

Machines and movement ratio (velocity ratio).

### Pneumatic Cylinder - Excerted Force vs. Pressure

Force excerted by pneumatic air cylinders vs. air pressure cylinder size - online calculator.

### Pulleys

Pulleys, blocks and tackles.

### Screw Jack - Effort Force vs. Load

Screw jacks and effort forces.

### Toggle Joint

A toggle joint mechanism can be used to multiply force.