OCR A-Level Physics/Equation Sheet

Equations, constants, and other useful data. Equations and constants are given in the formulae booklet unless stated otherwise.

AS Formulae

Unit 1 - Mechanics

$\text{efficiency}=\frac{\text{useful energy output}}{\text{total energy input}}\times 100\mathrm{\%}$

Kinematics Equations

• $v=u+at$
• $a=\frac{\mathrm{\Delta }v}{\mathrm{\Delta }t}=\frac{v-u}{t}$
• $s=\frac{1}{2}(u+v)t$
• $s=ut+\frac{1}{2}a{t}^2$
• $v^2=u^2+2as$

Forces, Moments and Pressure

• $F_x=Fcos\theta$
• $F_y=Fsin\theta$
• $F=ma$
• $W=mg$
• $\text{moment}=Fx$
• $\text{torque}=Fd$
• $\rho =\frac{m}{V}$
• $p=\frac{F}{A}$

Work, Energy and Power

• $W=F_{x}cos\theta$
• $E_k=\frac{1}{2}m{v}^2$
• $E_p=mgh$
• $P=\frac{\mathrm{\Delta }W}{\mathrm{\Delta }t}$ Not given in formulae booklet.

Deforming Solids

• $F=kx$
• $E=\frac{1}{2}Fx=\frac{1}{2}k{x}^2$
• $\text{stress}=\frac{F}{A}$
• $\text{strain}=\frac{x}{L}$
• $\text{Young modulus}=\frac{\text{stress}}{\text{strain}}$

Unit 2 - Electrons, Waves and Photons

Electricity

• $\mathrm{\Delta }Q=I\mathrm{\Delta }t$
• $I=Anev$
• $W=VQ$
• $V=IR$
• $R=\frac{\rho L}{A}$
• $P=VI=I^{2}R=\frac{V^2}{R}$
• $W=VIt$
• $e.m.f=V+Ir$
• $V_{\text{out}}=\frac{R_2}{R_1+R_2}\times V_{\text{in}}$
• $R=R_1+R_2+\cdots$
• $\frac{1}{R}=\frac{1}{R_1}+\frac{1}{R_2}+\cdots$
  • If there are only two resistors, this simplified equation can be used which isn't given in booklet:
    $R=\frac{R_1{R}_2}{R_1+R_2}$

Waves and Photons

• $f=\frac{1}{T}$ This is NOT given in the unit 2 section of the booklet but IS given in the unit 4 section.
• $v=f\lambda$
• $\lambda =\frac{ax}{D}$
• $E=hf=\frac{hc}{\lambda }$
• $hf=\varphi +K{E}_{\text{max}}$
• $\lambda =\frac{h}{mv}$
• $\text{intensity}=\frac{\text{power}}{\text{cross-section area}}$
• The following equations are NOT given in the formulae booklet
  • $\text{intensity}\propto {\text{amplitude}}^2$
  • The following equation is known as Malus's Law:
    • $I=I_{0}co{s}^2\theta$
  • Malus's Law can also be given in terms of amplitude:
    • $A=A_{0}co{s}^2\theta$