How do Newton's laws and the quantities of linear motion describe and explain movement in sport?
Linear motion: Newton's three laws applied to sport, the linear quantities (distance, displacement, speed, velocity, acceleration), and the calculation and use of force, momentum and impulse from a force-time graph.
A focused answer to Eduqas A-Level PE on linear motion: Newton's three laws applied to sport, the linear quantities (distance, displacement, speed, velocity, acceleration), and the calculation of force, momentum and impulse with the impulse-momentum relationship read from a force-time graph.
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What this dot point is asking
Eduqas wants you to state and apply Newton's three laws to sport, define the quantities of linear motion, and calculate force (), momentum and impulse, using the impulse-momentum relationship and the area under a force-time graph.
Newton's three laws
The quantities of linear motion
For example, a sprinter whose velocity rises from to m/s in s has an acceleration of m/s squared.
Force and momentum
An kg rugby player moving at m/s has a momentum of kg m/s, far more than a kg player at the same speed, which is why the heavier player is harder to tackle.
Impulse and the impulse-momentum relationship
Distance-time and velocity-time graphs
Eduqas also expects you to read motion graphs. On a distance-time graph, the gradient is the speed (a steeper line is faster; a flat line is stationary). On a velocity-time graph, the gradient is the acceleration (a positive slope is speeding up, a flat line is constant velocity), and the area under the line is the distance travelled. Reading these correctly is worth marks in data-response questions.
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 20193 marksAn 80 kg rugby player accelerates at 3.5 m/s squared. Calculate the horizontal force they produce, give the unit, and state which of Newton's laws this illustrates.Show worked answer →
A Component 1 calculation. One mark for the value, one for the unit, one for the law.
Use Newton's second law , so N. The unit is newtons (N). This illustrates Newton's second law (the law of acceleration): the force produced is proportional to the rate of change of momentum, so a greater force gives a greater acceleration for a given mass.
A common dropped mark is omitting the unit or naming the wrong law; is the second law.
Eduqas 20216 marksFigure 1 shows a force-time graph for a long jumper's take-off foot, with a small negative phase followed by a larger positive phase. Define impulse, and explain how the graph relates to the jumper generating vertical velocity for take-off.Show worked answer →
A Component 1 data-response question. Markers reward defining impulse and reading the graph.
Award marks for: impulse is the product of force and the time it acts, , measured in newton-seconds (Ns), and it equals the change in momentum. On the graph, the area under the curve is the impulse. The small negative phase at touchdown is a braking impulse that slightly slows the jumper; the larger positive phase is a propulsive (upward and forward) impulse generated by the leg drive. Because the positive area exceeds the negative area, the net impulse is positive, producing a positive change in momentum, so the jumper gains the upward velocity needed for take-off. A larger net impulse (more force, or a longer time on the board) gives a greater take-off velocity and a longer jump.
A top answer links the net positive area to the change in momentum and the take-off velocity, not just describes the graph.
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Sources & how we know this
- Eduqas A Level Physical Education Specification — Eduqas (2016)