# OCR A-Level Physics/Equation Sheet

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

## AS Formulae

### Unit 1 - Mechanics

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

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

• $W=F_{x}cos\theta$ • $E_{k}={\frac {1}{2}}mv^{2}$ • $E_{p}=mgh\$ • $P={\frac {\Delta W}{\Delta t}}$ Not given in formulae booklet.

#### Deforming Solids

• $F=kx$ • $E={\frac {1}{2}}Fx={\frac {1}{2}}kx^{2}$ • ${\text{stress}}={\frac {F}{A}}$ • ${\text{strain}}={\frac {x}{L}}$ • ${\text{Young modulus}}={\frac {\text{stress}}{\text{strain}}}$ ### Unit 2 - Electrons, Waves and Photons

#### Electricity

• $\Delta Q=I\Delta t$ • $I=Anev$ • $W=VQ$ • $V=IR$ • $R={\frac {\rho L}{A}}$ • $P=VI=I^{2}R={\frac {V^{2}}{R}}$ • $W=VIt$ • $e.m.f=V+Ir$ • $V_{\text{out}}={\frac {R_{2}}{R_{1}+R_{2}}}\times V_{\text{in}}$ • $R=R_{1}+R_{2}+\cdots$ • ${\frac {1}{R}}={\frac {1}{R_{1}}}+{\frac {1}{R_{2}}}+\cdots$ • 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.
• $v=f\lambda$ • $\lambda ={\frac {ax}{D}}$ • $E=hf={\frac {hc}{\lambda }}$ • $hf=\phi +KE_{\text{max}}$ • $\lambda ={\frac {h}{mv}}$ • The following equations are NOT given in the formulae booklet
• ${\text{intensity}}={\frac {\text{power}}{\text{cross-section area}}}$ • ${\text{intensity}}\propto {\text{amplitude}}^{2}$ • The following equation is known as Malus's Law:
• $I=I_{0}cos^{2}{\theta }$ • Malus's Law can also be given in terms of amplitude:
• $A=A_{0}cos^{2}{\theta }$ 