Resistance force
In physics
Physics is a natural science that involves the study of matter and its motion through spacetime, along with related concepts such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves.Physics is one of the oldest academic...

, resistance force is the force
In physics, a force is any influence that causes an object to undergo a change in speed, a change in direction, or a change in shape. In other words, a force is that which can cause an object with mass to change its velocity , i.e., to accelerate, or which can cause a flexible object to deform...

 which an effort force must overcome in order to do work
Mechanical work
In physics, work is a scalar quantity that can be described as the product of a force times the distance through which it acts, and it is called the work of the force. Only the component of a force in the direction of the movement of its point of application does work...

 on an object via a simple machine
Simple machine
A simple machine is a mechanical device that changes the direction or magnitude of a force.In general, they can be defined as the simplest mechanisms that use mechanical advantage to multiply force. A simple machine uses a single applied force to do work against a single load force...

. Resistance force, like most other forces, is measured in newtons or in pounds-force.

For an ideal (friction
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and/or material elements sliding against each other. There are several types of friction:...

less) mechanism in which no energy
In physics, energy is an indirectly observed quantity. It is often understood as the ability a physical system has to do work on other physical systems...

 is lost, resistance force obeys the relation:

R equals resistance force
DR equals resistance distance
E equals effort force
DE equals effort distance

Resistance force is used to calculate the work output
Work output
In physics, work output is the work done by a simple machine, compound machine, or any type of engine model. In common terms, it is the energy output, which for simple machines is always less than the energy input, even though the forces may be drastically different.In thermodynamics, work output...

using the following equation:
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