### KS3 Biology

Cells and Organisation
Nutrition and Digestion
Gas Exchange Systems
Reproduction
Health
Genetics and Evolution
Material Cycles and Energy
Relationships in an Ecosystem

# Biomechanics

Biomechanics Biomechanics is the study of human movement, analysing the forces that act on the body. It explores both the mechanics of how and why the body moves, as well as the relationship between bones and muscles.

To understand how force generates movement in the body, it’s important to know what a ‘pivot’ and a ‘lever’ are:

• Pivot – A point around which something rotates or turns
• Lever – A bar that pivots around a fixed point

When a force acts on an object with a pivot, it generates a turning effect called a moment. Pivots, levers and moments are often involved when forces act on the body. For example, your arm functions as a lever with the elbow serving as the pivot. When a force acts on your arm, it creates a moment.

We can calculate the moment of a force by using the equation:

• M = Moment in newton metres (Nm)
• F = Force in newtons (N)
• d = Distance in metres (m)

Therefore, the moment is calculated by multiplying the force by the distance from the pivot point to the line of action of the force, measured perpendicularly. Perpendicular distance is the distance at a right angle from the pivot to the line of force.

## Example

The diagram below shows that the weight in the hand, which is a force, creates a moment when it is applied around the pivot point.

Calculate the moment of the force.

Weight (force) = 12 N

Distance from the pivot point = 0.3 m

• M (Moment) = F (Force) × d (Distance)
• M = 12 N × 0.3 m
• M = 3.6 N·m

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