Balance and stability
This term describes the area beneath a person or object that is in contact with a supporting surface.
Base of support. It is the area on which a person or object rests, and a larger base of support generally means greater stability.
What is a trajectory?
The path along which a projectile travels.
Name the three parts of a lever.
The fulcrum (pivot point), the effort (force applied), and the load (resistance being moved).
In simple terms, this is the definition of a force.
What is a push or pull that occurs when two objects interact?
A shot put has a mass of 4 kg and accelerates at 6 m/s². Calculate the force applied.
What is 24 N? (F = m × a → 4 × 6 = 24)
Describe the difference between static balance and dynamic balance
Static balance is maintaining equilibrium when the body is stationary. Dynamic balance is maintaining equilibrium while the body is moving.
Name the two external forces that affect every projectile and describe what each one does.
Gravitational force pulls the projectile down toward Earth. Drag force (air resistance) opposes the projectile's movement and slows it down.
Match each lever class to its everyday example: see-saw, tweezers, and wheelbarrow.
See-saw = first class (fulcrum in the middle). Wheelbarrow = second class (load in the middle). Tweezers = third class (effort in the middle).
Name the TWO broad categories of force, and give one example of each.
What are internal forces (e.g. muscles contracting) and external forces (e.g. gravity, friction)?
A gym sled weighs 60 kg and moves at 3 m/s. Calculate its momentum.
What is 180 kg m/s? (p = m × v → 60 × 3 = 180)
A wrestler wants to resist being pushed sideways. Describe two adjustments they should make to maximise their stability, and explain the biomechanical reason for each.
1) Widen their stance — this increases the base of support side-to-side so the line of gravity stays within it. 2) Lower their centre of gravity by bending their knees — a lower centre of gravity means the body must be displaced further before losing balance.
A shot putter wants to maximise their throwing distance. What is the optimal angle of release and why does it differ from the theoretical 45°?
The optimal angle is roughly 37–43°, not 45°, because the shot is released from above the ground (height of release). A higher release point means a slightly lower angle achieves maximum distance.
When a basketball player rises up on the balls of their feet to jump, which class of lever is working in their ankle? Identify the fulcrum, load and effort.
Second-class lever. The fulcrum is the toes (ball of the foot), the load is the body weight in the middle, and the effort is the calf muscle pulling up at the heel.
A lawn bowl slows as it rolls across the green. A swimmer slows moving through water. Name the contact force responsible for each.
What are friction force (lawn bowl) and drag force (swimmer)?
Name TWO of THREE biomechanical concepts that combine to produce force.
What are momentum, summation of forces, and impulse?
Explain how a high jumper using the Fosbury Flop technique manipulates their centre of gravity to improve efficiency, and why this is biomechanically advantageous.
By arching their back as they clear the bar, the high jumper bends their body so that their centre of gravity passes below the bar even though their body goes over it. This means they do not need to raise their centre of gravity as high as the bar itself, requiring less energy and allowing them to clear greater heights.
Two basketball players of different heights shoot a free throw at the same speed. Explain why the shorter player needs a higher angle of release to match the taller player's range.
The taller player has a greater height of release, so their ball stays in the air longer, travelling further at a lower angle. The shorter player must compensate with a higher angle to increase hang time and cover the same distance.
A cricket bat and a diving board are both levers used in sport. Explain why one is a speed multiplier and the other is a force multiplier.
A cricket bat is a speed multiplier — it extends the arm's resistance arm, so the end of the bat travels faster than the hand, increasing the speed of the ball. A diving board is a force multiplier — its long force arm allows the diver to generate more force from less effort, producing greater jump height.
A rugby player drops the ball after being tackled and it keeps moving forward. A tennis ball briefly changes shape on impact before returning to normal. Name the contact force shown in each.
What are inertial force (ball keeps moving) and elastic force (ball returns to shape)?
In sequential summation of forces, which body parts move FIRST and which move LAST? Give a sport example.
What is larger, stronger, slower body parts first (e.g. legs and torso), followed by smaller, lighter, faster parts last (e.g. arms, wrist, fingers) — e.g. a discus throw or netball shot?
A sumo wrestler and a 100m sprinter both need stability at different points in their event. Using the factors that affect stability, explain why their body positions at the start of their performance look so different.
The sumo wrestler widens their base of support, lowers their centre of gravity by bending their knees, and uses their greater mass — all maximising stability to resist force. The sprinter uses a narrow, forward-leaning start that deliberately shifts the line of gravity toward the front edge of their base, reducing stability to initiate explosive forward movement. Same principles, opposite goals.
A javelin thrower can either release at the optimal 40° angle with moderate speed, or drop to 32° with much greater speed. Which should they choose and why?
Speed of release is the most influential factor on distance, so the lower angle with greater speed is likely better. Greater horizontal velocity directly increases distance, and the trade-off in hang time at 32° is outweighed by the gain in release velocity — which is why elite throwers typically release between 32° and 36°.
A taller and a shorter athlete both compete in javelin. Using your knowledge of anatomical levers, explain one advantage each athlete has.
The taller athlete has longer anatomical levers, generating greater speed and force at the end of the arm — useful for throwing distance. The shorter athlete has shorter levers that are easier to accelerate and control, and they can compensate through superior technique, such as better summation of forces and momentum transfer.
Name the TWO types of external forces and give one sport example of each.
What are contact forces (e.g. friction when a sprinter pushes off the ground) and non-contact forces (e.g. gravitational force pulling a gymnast back to the ground)?
A bowling ball hits stationary pins and slows down. The pins begin to move. What principle explains this, and what happens to the total momentum?
What is conservation of momentum? The momentum is not lost — it is transferred from the bowling ball to the pins. The total combined momentum before and after the collision remains the same.