Syllabus coverage
- Sketch the vector (horizontal and vertical) components of flight
- Explain the vector (horizontal and vertical) components of flight
- Explain the factors that affect the flight paths of different objects, including the parabolic flight of a shot put and the non-parabolic flight of a badminton shuttlecock
- Explain the factors that affect the horizontal displacement of objects, limited to height of release, speed of release and angle of release
Part of the AS Level PE 8386 syllabus 8386.
Flight is two motions happening at the same time
A projectile is any object that is given an initial force and then travels through the air under the influence of gravity. A shot put, a shuttlecock and a cricket ball in flight are all projectiles.
Its flight has a horizontal component and a vertical component, and these behave differently. Treat them separately and every flight-path question becomes manageable.
| Component | What it does after release | Why |
|---|---|---|
| Horizontal | Travels a constant distance in each equal time interval — constant horizontal velocity | Once the thrower lets go, no horizontal force acts on the object (air resistance ignored), so there is nothing to speed it up or slow it down |
| Vertical | Decelerates on the way up, stops momentarily at the top, then accelerates on the way down | Gravity acts vertically downwards throughout flight, so velocity upwards decreases and then velocity downwards increases |
Parabolic flight: the shot put
A parabolic flight path is a symmetrical curve: the object rises and falls in equal but opposite arcs, and it travels the same horizontal distance in equal time intervals.
The shot put is the syllabus's example. It is heavy and compact, so it has a large mass for its surface area. The air resistance acting on it is negligible compared with its momentum, so once it leaves the hand gravity is effectively the only force acting on it. Gravity pulls it down at a constant rate, and the constant horizontal velocity carries it forward — the result is a symmetrical parabola.
- Constant horizontal velocity → equal horizontal distances in equal times
- Gravity only, so the vertical motion is symmetrical up and down
- The flight path is a smooth symmetrical curve
Non-parabolic flight: the badminton shuttlecock
A non-parabolic flight path is asymmetrical. The shuttlecock rises quickly, is then heavily slowed by air resistance, drops almost vertically, and lands much closer to the player than a parabola would predict.
The reason is the shuttlecock's shape and mass. It is very light with a large, cone-shaped skirt, so it has a large surface area relative to its mass. Air resistance (drag) is therefore large compared with its momentum: it decelerates sharply in flight as well as falling under gravity. The extra, non-vertical force means the path is no longer a symmetrical curve.
| Object | Mass compared with surface area | Air resistance in flight | Flight path |
|---|---|---|---|
| Shot put | Large mass, small surface area, streamlined | Negligible — it does not noticeably slow the shot | Parabolic (symmetrical) |
| Badminton shuttlecock | Small mass, large surface area (feathered skirt) | Large — it decelerates quickly during flight | Non-parabolic (asymmetrical, drops steeply) |
Other factors that change a flight path
Aside from gravity and air resistance, two further factors are useful for explaining why real flight paths deviate from a perfect parabola: the shape of the object and spin.
Shape controls how much air resistance the object meets. A smooth, streamlined shot put or a discus cuts through the air, while a shuttlecock's cone or a table tennis ball's hollow, lightweight body is slowed far more. Mass works alongside shape: two objects of the same shape behave differently if one is much heavier, because the heavier object has more momentum and so resists the slowing effect of drag.
Spin changes the flight path by altering the airflow around the object — the Magnus effect. A ball with backspin experiences higher pressure above it and lower pressure beneath it, so it stays in the air longer and travels further; topspin reverses that and makes the ball dip more sharply. Tennis and table tennis players use spin deliberately for exactly this reason.
What changes how far an object travels
Horizontal displacement (the overall distance travelled) is affected by exactly three release factors. Learn them as a set of three — a four-mark question on this is usually one mark for each factor plus one for explaining it.
| Factor | What happens | Sporting example |
|---|---|---|
| Height of release | The higher the release point, the further the object travels, because it stays in the air for longer and the vertical component has further to fall | A basketballer releasing a shot from above head height; a shot putter who is tall or who releases above shoulder level |
| Speed of release | The greater the speed of release, the greater the horizontal velocity and the further the object travels for any given angle | A shot putter driving hard through the legs and hips at the moment of release to maximise release speed |
| Angle of release | The optimum angle of release depends on the other two factors. When release and landing heights are equal, 45° maximises horizontal displacement. When release height is above landing height, a flatter angle (below 45°) is more effective | A shot putter releasing at around 40° rather than 45°, because the shot leaves the shoulder above the ground it lands on |
Turning this into sporting decisions
These factors are what coaches actually manipulate. In throwing events the aim is maximum horizontal displacement, so release speed is built through technique and strength, and the release angle is chosen to suit the thrower's height of release.
In badminton the aim is the opposite: control, not distance. A high clear needs a steep release angle to send the shuttlecock deep, while a drop shot needs the player to take speed off the shuttlecock, letting air resistance pull it down sharply just over the net. Because the shuttlecock's path is non-parabolic, players can judge its landing point far more easily than a ball's.
Key terms you must be able to define
- Projectile
- An object given an initial force that then travels through the air under the influence of gravity.
- Parabolic flight
- A symmetrical flight path in which the object rises and falls in equal but opposite arcs, created when gravity is effectively the only force acting during flight.
- Non-parabolic flight
- An asymmetrical flight path in which air resistance also acts on the object, so it decelerates in flight and drops more steeply than a parabola.
- Horizontal component
- The forward part of the projectile's velocity, which remains constant during flight if air resistance is ignored.
- Vertical component
- The upward/downward part of the projectile's velocity, which decreases as the object rises and increases as it falls because of gravity.
- Air resistance (drag)
- The resistance caused by air particles colliding with a moving object; larger when the object's surface area is large relative to its mass.
- Height of release
- The vertical height above the ground at which the projectile leaves the body or implement; a greater height of release increases horizontal displacement.
- Speed of release
- How fast the projectile is travelling as it leaves the body or implement; a greater speed of release increases horizontal displacement.
- Angle of release
- The angle between the projectile's direction of travel at release and the horizontal; it works with height and speed of release to determine displacement.
- Magnus effect
- The change in a projectile's flight path caused by spin, which alters the pressure of the air moving over and under the object.
Applied to your sport
Cambridge requires you to apply this knowledge to physical activities. Use these as models, then write your own for the sport you play.
A shot put travels in a symmetrical parabola. The putter increases horizontal displacement by driving hard through the legs to raise release speed and releasing at an angle slightly below 45°, because the shot leaves the hand above head height.
The shuttlecock's large feathered skirt and tiny mass make air resistance dominant, so its path is non-parabolic. A high clear needs a steep angle of release to clear the opponent's reach, and even a hard hit slows noticeably before landing.
A heavily topped ball dips on to the table far earlier than a parabola would predict, while backspin keeps the ball in the air longer — both are uses of spin to alter the flight path.
A long throw or a floated clearance is slowed by air resistance on the way down, so the player must judge the horizontal and vertical components separately; a driven shot with minimal spin holds a flatter path than a curled shot.
Flashcards
Click a card to flip it. Mark honestly — the tracker uses this.
Exam-style questions
7 questions, 20 marks. Write your answer, then reveal the mark scheme and tick each point you actually made. Answering honestly here is what makes the rest of the site useful.
Mark scheme — tick each point you actually made
Mark scheme — tick each point you actually made
Mark scheme — tick each point you actually made
Mark scheme — tick each point you actually made
Mark scheme — tick each point you actually made
Mark scheme — tick each point you actually made
Mark scheme — tick each point you actually made
Exam technique for this topic
- When asked to sketch flight vectors, draw the horizontal and vertical arrows at the point of release and keep them at right angles to each other — Cambridge awards the marks for the two separate components, not for the curved path.
- For any explain question about flight paths, name the factor and then say what it does: "Air resistance is large on the shuttlecock because it has a large surface area for its mass, so it decelerates in flight and its path becomes non-parabolic."
- Learn the three release factors as a set of three. Almost every displacement question can be answered by working through height, speed and angle.
- Do not write "45°" on its own when the question mentions a release height above landing height — explain that the optimum angle is lower when the thrower releases from above ground level.
- Ignore air resistance unless the question is about a light or large-surface-area object, and say that you are ignoring it. That is what lets you describe a shot put as parabolic.