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# Force Ratio

## The force ratio is the load force versus the effort force.

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

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

Fr = F / S                             (1)

where

Fr = force ratio - mechanical advantage

F = load force (N, lbf)

S = effort force (N, lbf)

### 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

Fr = (100 kg) (9.81 m/s2) / (245 N)

= 4

## Related Topics

• ### Mechanics

Forces, acceleration, displacement, vectors, motion, momentum, energy of objects and more.

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Acceleration of gravity and Newton's Second Law - SI and Imperial units.
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Forces due to circular motion and centripetal / centrifugal acceleration.
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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.
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Gears effort force vs. load force.
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• ### Impulse and Impulse Force

Forces acting a very short time are called impulse forces.
• ### Levers

Use levers to magnify forces.
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Pulley (Sheave) selection charts for motors ranging 850 - 3450 rpm.
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Machines and movement ratio (velocity ratio).
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Force excerted by pneumatic air cylinders vs. air pressure cylinder size - online calculator.
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Screw jacks and effort forces.
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A toggle joint mechanism can be used to multiply force.

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## Citation

• The Engineering ToolBox (2008). Force Ratio. [online] Available at: https://www.engineeringtoolbox.com/force-ratio-d_1294.html [Accessed Day Month Year].

Modify the access date according your visit.

9.29.12