Explain the factors affecting the flight path of a projectile, including angle, speed and height of release

What this dot point is asking

SEAB wants you to explain the factors that affect the flight path of a projectile and why a projectile follows a curved path. The central idea is that once an object is released into the air, only its release conditions and gravity (plus air resistance) decide where it lands, so athletes shape the throw, kick or jump to control distance and height.

The answer

What a projectile is

A projectile is any object launched into the air that then moves under the influence of gravity. In sport this includes a thrown javelin, a struck football, a shot put, a long jumper's body and a served tennis ball.

The factors affecting flight path

Three release factors decide how far and high a projectile travels.

• Speed of release: the faster the projectile leaves, the further and higher it goes, because it travels more before gravity brings it down. This is usually the most important factor for distance.
• Angle of release: there is an optimum angle for maximum distance. When the release and landing heights are equal, this is about 45 degrees; angles too steep or too shallow give less distance.
• Height of release: a higher release point increases the flight time, so the projectile travels further before landing. This is why a tall shot putter has an advantage.

A fourth influence, air resistance, slows a projectile and reduces its distance, and matters more for light objects with a large surface.

Why the path is curved

After release, two things act on the projectile at once:

• its forward motion carries it horizontally at a roughly constant speed;
• gravity pulls it downward, so it accelerates toward the ground.

Combining steady horizontal motion with increasing downward motion produces a smooth curve called a parabola: the projectile rises, slows its rise, then falls. It never travels in a straight line once released.

Examples in context

Example 1. A long jumper at take-off. The jumper maximises horizontal speed on the runway and takes off at an angle well below 45 degrees, because their body is released and lands at roughly the same height but speed is hard to keep at steep angles. The flight of the body follows a parabola until landing.

Example 2. A goal kick in football. The kicker chooses the angle to balance distance and flight time: a flatter, faster kick travels far quickly, while a steeper kick gains height and hang time but less distance. Both follow a parabolic path shaped by release speed, angle and gravity.

Try this

• Cue. State the three release factors that affect how far a projectile travels. (Speed of release, angle of release and height of release.)

• Cue. Explain why the optimum release angle for a shot put is slightly below 45 degrees. (The shot is released above the ground but lands on it, so the heights are unequal, which lowers the optimum angle from 45 degrees.)

• Cue. Describe the two influences that make a thrown ball follow a curved path. (Constant horizontal motion combined with gravity's downward acceleration produces a parabola.)