# OCR A-Level Physics/Equation Sheet

(Redirected from 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

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

#### Kinematics Equations

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

#### Forces, Moments and Pressure

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

#### Work, Energy and Power

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

#### Deforming Solids

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

### Unit 2 - Electrons, Waves and Photons

#### Electricity

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

#### Waves and Photons

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