Work, Energy and Power: CDS Physics

Formulas (3)

• Work done by a force · Work done by a constant force
  $$W = Fs\cos\theta$$
• Kinetic and potential energy · Kinetic and potential energy
  $$K = \tfrac{1}{2}mv^{2} = \dfrac{p^{2}}{2m} \qquad U = mgh \qquad K + U = \text{constant} \qquad v = \sqrt{2gh}$$
• Power · Power
  $$P = \dfrac{W}{t} \qquad P_{\text{lift}} = \dfrac{mgh}{t} \qquad 1\ \text{kWh} = 3.6 \times 10^{6}\ \text{J}$$

Watch out for (6)

• Effort is not work
  → Work done by a force
• A centre-pointing force does no work
  → Work done by a force
• Kinetic energy follows the square
  → Kinetic and potential energy
• Lowest point, least potential energy
  → Kinetic and potential energy
• kW is power, kWh is energy
  → Power
• Least power uses the potential energy gained
  → Power