How do mass, weight, levers, centre of mass and stability govern efficient sporting movement?
Biomechanical principles: mass, weight, inertia and friction, the lever systems and mechanical advantage, the centre of mass, and the factors affecting stability and balance.
A focused answer to Eduqas A-Level PE on biomechanical principles: mass, weight and inertia, friction, the three lever systems and mechanical advantage with calculation, the centre of mass, and the four factors affecting stability and balance in sport.
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What this dot point is asking
Eduqas wants you to define mass, weight, inertia and friction, describe the three lever systems and calculate mechanical advantage, locate the centre of mass, and explain the factors affecting stability and balance.
Mass, weight, inertia and friction
The lever systems
Mechanical advantage
Centre of mass and stability
Exam-style practice questions
Practice questions written in the style of WJEC Eduqas exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
Eduqas 20194 marksA performer rises onto tiptoes (plantarflexion at the ankle). Identify the class of lever operating, name the fulcrum, effort and load, and state its mechanical advantage characteristic.Show worked answer →
A Component 1 lever question. One mark each for the class, the three components, and the mechanical advantage point.
Rising onto tiptoes uses a second-class lever at the ankle. The fulcrum is the ball of the foot (the metatarsals on the ground), the load is the body weight acting down through the ankle joint (in the middle), and the effort is the pull of the calf muscles (gastrocnemius and soleus) via the Achilles tendon at the heel. Because the load is between the fulcrum and the effort, the effort arm is longer than the load arm, so the mechanical advantage is greater than 1: a small muscular effort moves a large load (the body weight). This favours force over range.
A common dropped mark is naming the wrong class; the ankle in plantarflexion is the body's main second-class lever.
Eduqas 20226 marksExplain the four factors that affect stability, and apply them to compare a sprinter in the set position with a judo player resisting being thrown.Show worked answer →
A Component 1 stability question. Markers reward the four factors and a comparison of two performers.
Award marks for: stability increases with (1) a lower centre of mass, (2) a larger base of support, (3) the line of gravity falling centrally within the base, and (4) a greater mass. A judo player resisting a throw wants maximum stability: they lower their centre of mass by bending the knees, widen their base by spreading the feet, keep the line of gravity central over the base, and a greater body mass helps them resist. A sprinter in the set position wants the opposite, low stability, so they can react and drive forward quickly: they raise the hips so the centre of mass is high and the line of gravity is near the front edge of the base, making them deliberately unstable and ready to move. So the same four factors are manipulated in opposite directions depending on whether the aim is to resist movement or to initiate it.
A top answer applies all four factors and explains that stability is reduced on purpose when quick movement is the goal.
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Sources & how we know this
- Eduqas A Level Physical Education Specification — Eduqas (2016)