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

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

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.
• $v=f\lambda$
• $\lambda ={\frac {ax}{D}}$
• $E=hf={\frac {hc}{\lambda }}$
• $hf=\phi +KE_{\text{max}}$
• $\lambda ={\frac {h}{mv}}$
• ${\text{intensity}}={\frac {\text{power}}{\text{cross-section area}}}$
• 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:
    • $I=I_{0}cos^{2}{\theta }$
  • Malus's Law can also be given in terms of amplitude:
    • $A=A_{0}cos^{2}{\theta }$