Mechanical Advantage in Sport (AQA GCSE Physical Education (PE))
Revision Note
Author
Ruth BrindleExpertise
Biology
Mechanical Advantage in Relation to the Three Lever Systems
Different types of levers in the human body offer different mechanical advantages, enhancing efficiency and effectiveness in different types of movement
First and third class levers have an effort arm that is short compared to the resistance arm
This enables:
Fast movement
A wide range of movement
E.g. the biceps acting to pull up the lower arm around the elbow joint as an example of a third class lever
Mechanical advantage in first and third class levers diagram
In a first and third class lever the effort arm is shorter than the resistance arm
Second class levers have a long effort arm compared to the length of the resistance arm
This allows joints to overcome a large resistance with relatively little effort
E.g. the gastrocnemius muscle acting to lift body weight around the ankle joint as a fulcrum
Mechanical advantage in second class levers diagram
In a second class lever the effort arm is longer than the resistance arm
Calculating mechanical advantage
We can calculate the mechanical advantage by measuring the length of the effort arm and the resistance arm and applying the following equation
mechanical advantage = effort arm length ÷ weight (resistance) arm length
Worked Example
The image below shows three different levers, labelled A, B and C.
Identify which of A, B or C represents a second class lever with the biggest mechanical advantage. Justify your answer
B shows a second class lever with the biggest mechanical advantage
Justification:
B is a second class lever as the resistance, or load, is located in the centre / between the fulcrum and the effort
B shows the biggest mechanical advantage because the length of the effort arm is the longest in relation to the length of the resistance arm
Exam Tip
You need to be able to label the effort arm and the resistance arm on lever drawings and determine the mechanical advantage of that lever.
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