How to calculate effort & force

Written by michael o. smathers
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How to calculate effort & force
A spring scale measures the weight of an object. (scale image by Pontus Edenberg from

To determine the mechanical efficiency of a machine, you need to determine the output force and the effort force, or the force you exert on the machine to cause it to do its work. Mechanical efficiency is the ratio of input force to output force. You may also need to calculate the effort force to do work without machines being involved.

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Things you need

  • Calculator
  • Spring scale
  • Protractor

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  1. 1

    Divide the object's weight by 9.8 to determine the minimal amount of upward effort force needed to counteract gravitational pull.

  2. 2

    To determine the force needed to move an object horizontally along a surface, multiply its weight by the coefficient of friction. To find the coefficient of friction when this quantity is unknown, weigh the mass, record the result and record the amount of force needed to move the mass. According to Georgia State University, the coefficient of friction varies by the roughness of the object and the surface on which it rests, and represents conditions at the threshold of motion.

  3. 3

    Calculate the effort force necessary to accelerate an object up an inclined plane by using the equation W=(Sina + ucosA), where W represents the object's weight, A represents the angle of the incline and u represents the coefficient of static friction at the threshold of motion.

  4. 4

    Calculate the effort force needed to operate a lever by multiplying the load force by the lever's load arm length, then dividing the result by the effort arm length.

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