3.4.1.4
Horizontal and vertical components of projectile motion are independent
Projectile Motion — AQA A-Level Physics
- The horizontal and vertical motions are completely independent of each other.
- They share only one common variable: time.
- Horizontal: $accelerationThe rate of change of velocityThe rate of change of displacement. A vector quantity. Measured in m s⁻¹.. A vector quantity. Measured in m s⁻². = 0$, so velocityThe rate of change of displacement. A vector quantity. Measured in m s⁻¹. is constant at u cos(theta).
- Vertical: $accelerationThe rate of change of velocityThe rate of change of displacement. A vector quantity. Measured in m s⁻¹.. A vector quantity. Measured in m s⁻². = g = 9.81 m s^-2 downwards$, so velocity changes.
- Solve each direction separately using SUVAT, then combine results.
$$u_x = u \cos \theta$$
- $u_x$: horizontal component of initial velocity (m s⁻¹)
- $u$: initial speed (m s⁻¹)
- $θ$: angle of projection to horizontal
$$u_y = u \sin \theta$$
- $u_y$: vertical component of initial velocity (m s⁻¹)
- $u$: initial speed (m s⁻¹)
- $θ$: angle of projection to horizontal