Key Equations
Motion & Kinematics - OCR A-Level Physics
On Data Sheet
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First SUVAT equation
$$v = u + at$$
- Where:
- $v$ = m \(s^{-1}\)
- $u$ = m \(s^{-1}\)
- $a$ = m \(s^{-2}\)
- $t$ = s
Use when you know u, a, t and want v (or rearrange). No s in this equation.
Second SUVAT equation
$$s = ut + \frac{1}{2}at^{2}$$
- Where:
- $s$ = m
- $u$ = m \(s^{-1}\)
- $a$ = m \(s^{-2}\)
- $t$ = s
Use when you know u, a, t and want s. No v in this equation.
Third SUVAT equation
$$v^{2} = u^{2} + 2as$$
- Where:
- $v$ = m \(s^{-1}\)
- $u$ = m \(s^{-1}\)
- $a$ = m \(s^{-2}\)
- $s$ = m
Use when you know u, a, s and want v, or when time is not given. No t in this equation.
Fourth SUVAT equation
$$s = \frac{(u + v)}{2} \times t$$
- Where:
- $s$ = m
- $u$ = m \(s^{-1}\)
- $v$ = m \(s^{-1}\)
- $t$ = s
Displacement equals average velocity times time. No a in this equation.
Horizontal component of velocity
$$v_{x} = u\cos\theta$$
- Where:
- $v_x$ = m \(s^{-1}\)
- $u$ = m \(s^{-1}\)
Used in projectile problems. The horizontal velocity is constant throughout the flight (no horizontal acceleration).
Vertical component of velocity
$$v_{y} = u\sin\theta$$
- Where:
- $v_y$ = m \(s^{-1}\)
- $u$ = m \(s^{-1}\)
Used in projectile problems. The vertical velocity changes due to gravitational acceleration g.
Average velocity
$$\bar{v} = \frac{\Delta s}{\Delta t}$$
- Where:
- $\bar{v}$ = m \(s^{-1}\)
- $\Delta s$ = m
- $\Delta t$ = s
Average velocity equals total displacement divided by total time.