Projectile Motion - 3.3

Movement of a body through the air following a curved flight path under the force of gravity

a body that is launched into the air losing contact with the ground surface, e.g. discus/long jumper

• can be an athlete, or equipment that an athlete may throw, hit or kick e.g. javelin or tennis ball

factors affecting the horizontal distance travelled:

1. speed of release

2. angle of release

3. height of release

4. aerodynamic factors (Bernoulli and Magnus)

horizontal distance is primarily affected by the speed of release

• newton’s 2nd law of acceleration, greater the force applied = greater change in momentum and therefore acceleration of the projectile

based on a projectile being released at the same speed from the ground:

• 90° - the projectile will accelerate vertically upwards and come straight back down, travelling 0m

• 45° - optimal angle to maximise horizontal distance

• greater than 45° (e.g. 60/75) - projectile reaches peak height too quickly and rapidly returns to the ground

• less than 45° (e.g. 30) - projectile does not achieve sufficient height to maximise flight time

45° is optimal angle for release if the release height and landing height are equal. However, if the height of the projectile release is higher or lower than the landing height, optimal angle will change

• release height is above the landing height (positive relative release height) E.G. javelin and shot - the optimal angle of release is less than 45 as the projectile already has increased flight time due to the increased height of release

• release height is below the landing height (negative relative release height) E.G. bunker shot in golf - the optimal angle of release is more than 45 as the projectile needs an increased flight time to overcome the obstacle

projectile follows a flight path determined by the relative size of the forces acting upon it. true flight path of a projectile unaffected by air resistance mirrors the mathematical shape of a parabola. flight paths are described relative to a parabolic shape.

• as air resistance increases, the more a projectile will deviate from a parabolic flight path

a flight path symmetrical about its highest point caused by the dominant weight force of a projectile

• if weight is the dominant force and air resistance is very small

• E.G. shot put has very high mass and travels through the air at a low velocity, small frontal cross-sectional area and smooth surface = air resistance small

a flight path asymmetrical about its highest point caused by the dominant force of air resistance on the projectile

• if air resistance is the dominant force and weight is very small

• E.G. a badminton shuttle has a very low mass and travels at high velocities with a relatively uneven surface, which increase air resistance