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Ramps are Simple Machines

by Ron Kurtus (30 June 2016)

A ramp is an inclined plane that allows you to move an object to a greater height with less force than is needed to simply lift the object. A ramp can also be used to ease an object from a higher to a lower height.

Although it has no moving parts, a ramp is still considered a simple machine. It is called an inclined plane since it is a flat surface at an angle. The ideal force mechanical advantage (MAF) of a ramp is the weight of the object divided by the force required to move it up the ramp.

Resistance from friction can affect the mechanical advantage of a ramp. Since the friction of sliding an object up a ramp can increase the force required, rollers or wheels are usually used to reduce the friction and increase the force mechanical advantage.

Questions you may have include:

This lesson will answer those questions.



Relationships of ramp components

When you push an object of weight w up a ramp or inclined plane, the input force or effort required is a function of the incline angle. Thus:

FI = w*sin(α)

FO = w

where

Note: We use small w to denote weight, while large W is work done.

Also note: The angle α must be greater than zero (α > 0). Otherwise there is no inclination, and the mechanical advantage becomes meaningless.

Pushing a load up a ramp

Pushing a load up a ramp

Force mechanical advantage

The force mechanical advantage of the ramp is:

MAF = FO/FI

MAF = w/w*sin(α)

MAF = 1/sin(α), provided α > 0

For example, when the angle of the ramp is α = 45°, the mechanical advantage is MAF = 1/0.707 = 1.414.

Note that speed and distance mechanical advantages are not really relevant with ramps.

Other factors

There can be other factors that affect the force mechanical advantage of a ramp. Friction can reduce the mechanical advantage. Rollers can be used to reduce the effect of friction.

Effect of friction

In the real world, there is friction that resists the motion.

Components related to friction

When an object is on a ramp, its weight can be broken into components, parallel and perpendicular to the surface of the inclined plane.

Relationships of ramp weight components

Relationships of ramp weight components

If w is the weight of the object, then

The friction equation is:

fr = μw*cos(α)

where

Mechanical advantage with friction

Friction between the ramp and the object will require a greater input or effort force to overcome the resistance. In order to obtain the desired output force for a machine with friction, the ideal input force or effort must be increased by the amount of friction. This will reduce the force mechanical advantage.

MA'F = FO/(FI + fr)

where

Insert values to MA'F

FO = w

FI = w*sin(α)

fr = μw*cos(α)

MA'F = w/[w*sin(α) + μw*cos(α)]

MA'F = w/w[sin(α) + μcos(α)]

Thus:

MA'F = 1/[sin(α) + μcos(α)]

This force mechanical advantage is independent of the weight of the object but dependent on the coefficient of friction.

Special case

When α = 0°, sin(α) = 0 and cos(α) = 1. Thus:

MA'F = 1/μ

Summary

A ramp is an inclined plane that allows you to move a heavy object to some height with less force than needed to lift the object. A ramp can also be used to ease an object to a lower height.

Although it has no moving parts, a ramp is still considered a simple machine. It is called an inclined plane since it is a flat surface at an angle. The force mechanical advantage (MAF) of a ramp is the weight of the object divided by the force required to move it up the ramp.

Resistance factors of inertia and friction can affect the mechanical advantage of a ramp. An accelerating object requires a force to overcome its inertia. Since the friction of sliding an object up a ramp can increase the force required, rollers or wheels are usually used to reduce the friction and increase the force mechanical advantage.


Climb the ramp to success


Resources and references

Ron Kurtus' Credentials

Websites

Inclined Plane - Wikipedia

Machines Resources

Books

Top-rated books on Simple Machines

Top-rated books on Machines


Questions and comments

Do you have any questions, comments, or opinions on this subject? If so, send an email with your feedback. I will try to get back to you as soon as possible.


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