What determines how far and how a projectile travels in sport?
Projectile motion in sport, the factors of release affecting horizontal distance, the forces of weight and air resistance, and the parabolic flight path.
A focused WJEC A-Level PE answer on projectile motion, covering the three release factors (speed, angle and height), the forces of weight and air resistance, the resolution of velocity into components, and the parabolic flight path.
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What this dot point is asking
WJEC wants you to explain projectile motion in sport: the three release factors that determine horizontal distance, how weight and air resistance act on a projectile, how velocity resolves into horizontal and vertical components, and why some flight paths are true parabolas and others are distorted.
The factors of release
These factors interact. A shot-putter who is taller (greater release height) can release at slightly under 45 degrees and still maximise distance, because the extra height buys flight time.
The forces on a projectile
Whether air resistance matters depends on the ratio of weight to air resistance. A heavy, dense, streamlined object (shot put, javelin) has a large weight and small air resistance, so weight dominates. A light object with a large surface area (shuttlecock, table-tennis ball) has a small weight and relatively large air resistance, so drag has a big effect.
Resolving velocity and the flight path
The release velocity can be resolved into two independent parts using a parallelogram or triangle of vectors: a horizontal component (which stays roughly constant if air resistance is small) and a vertical component (which decreases on the way up, reaches zero at the peak, and increases on the way down due to gravity).
- When weight dominates (dense object), the path is a symmetrical parabola: the ascent mirrors the descent.
- When air resistance is significant (light object), the path is asymmetrical and non-parabolic: the object slows and drops more steeply, so the descent is steeper than the ascent.
Examples in context
Example 1. The long jumper's take-off. A long jumper cannot reach the theoretical 45-degree optimum because they cannot generate enough vertical velocity at high horizontal speed, so they take off at around 20 degrees. WJEC uses this to show real release angles are constrained by what the body can produce.
Example 2. The badminton clear. A high clear in badminton drops almost vertically at the back of the court because air resistance rapidly slows the light shuttle, distorting the path. This contrasts directly with a javelin, where weight dominates and the path stays close to a parabola.
Try this
Q1. Name the three factors at release that affect the horizontal distance of a projectile. [3 marks]
- Cue. Speed (velocity) of release, angle of release, and height of release.
Q2. Explain why the optimum angle of release for a shot put is slightly less than 45 degrees. [2 marks]
- Cue. The shot is released from above the ground (release height greater than landing height), so a slightly lower angle maximises distance by using the extra flight time the release height provides.
Q3. Explain why a shot put follows a true parabola but a shuttlecock does not. [3 marks]
- Cue. A shot has a large weight and small air resistance, so weight dominates and the path is symmetrical; a shuttle is light with large air resistance, which distorts the path into an asymmetrical, steeper descent.
Exam-style practice questions
Practice questions written in the style of WJEC exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
WJEC 20184 marksState the three factors at the point of release that determine the horizontal distance a shot put travels, and explain the effect of each.Show worked answer →
The three factors are the speed (velocity) of release, the angle of release, and the height of release.
Speed of release: the greater the release velocity, the greater the horizontal distance, because the projectile travels further before landing.
Angle of release: there is an optimum angle. For an object released and landing at the same height, around 45 degrees is optimum; because the shot is released above the ground, the optimum is slightly less than 45 degrees.
Height of release: a greater release height increases horizontal distance because the projectile spends longer in flight before it lands.
Markers reward naming all three factors and a correct effect for each, including the idea that release above the ground lowers the optimum angle below 45 degrees.
WJEC 20204 marksExplain why the flight path of a shot put is described as a true parabola, whereas that of a badminton shuttle is not.Show worked answer →
A projectile's flight path depends on the balance of the forces acting on it: weight (gravity) always acts downward, and air resistance acts against the direction of motion.
For a dense, heavy object such as a shot put, weight is very large compared with air resistance, so air resistance has little effect and the flight path is a symmetrical (true) parabola.
For a light object with a large surface area, such as a badminton shuttle, air resistance is significant relative to its small weight, so it slows the shuttle markedly and distorts the path, giving an asymmetrical (non-parabolic) flight that drops more steeply.
Markers reward the role of weight versus air resistance, a large weight-to-air-resistance ratio giving a true parabola, and a small ratio giving a distorted, asymmetrical path.
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