In physics, any object moving freely under gravity is called a projectile.

By moving freely it is assumed there is no air resistance or other external forces. In practice many sports balls achieve lift due to spin.

The motion of projectiles must be analysed in terms of vertical and horizontal components.

Horizontal component

The horizontal component of velocity is constant speed (assuming no air resistance).

Projectiles - horizontal motion

Vertical component

The vertical component is acceleration downwards due to gravity (-9.8 ms-2 on Earth)

Projectiles - vertical motion

If the initial velocity is given as a speed and direction, this velocity vector must be resolved into two components by trigonometry.

The two components can allow the calculation of:

  • time of flight
  • maximum height reached
  • range – horizontal distance from launch to landing