ENERGY CHANGES IN A SYSTEM

• What is the equation for kinetic energy?

  $KE =$$\frac{1}{2} mv^2$
• What are the SI units for kinetic energy?

  Energy (J), Mass (kg), Velocity (m/s)
• What is the equation for elastic potential energy?

  $EPE =$$\frac{1}{2} kx^2$
• What are the SI units for elastic potential energy?

  Energy (J), Spring Constant (N/m), Extension (m)
• What is the equation for gravitational potential energy?

  $GPE =$$mgh$
• What are the SI units for gravitational potential energy?

  Energy (J), Mass (kg), Gravitational Field Strength (N/kg), Height (m)
• What is the definition of 'Specific Heat Capacity'?

  Energy needed to raise 1 kg by 1°C
• What are the units for Specific Heat Capacity?

  J/°C/kg
• What is the definition of 'Power'?

  The rate at which energy is transferred
• What is one equation for power?

  Power = energy transferred/time
• What is another equation for power?

  Power = work done/time
• What are the SI units for power?

  Energy (J), Work Done (J), Time (s)
• Which motor dissipates more power when lifting the same mass?

  Motor A
• What is the unit of power?

  Watt (W)
• Why does Motor A dissipate more power than Motor B?

  Time taken is less for Motor A
• What are the energy changes when a ball is thrown upwards and returns?

  • Upwards: KE to GPE
  • Peak: Maximum GPE, zero KE
  • Downwards: GPE to KE
• What are the energy transfers for a bungee jumper?

  • Falling: GPE to KE
  • Cord tightens: KE to EPE
  • Lowest point: Initial GPE equals EPE
• Why does a bungee jumper slow down when the cord stretches?

  KE decreases as it converts to EPE
• What are examples of chemical energy stores?

  Food, fuel, batteries
• What are the different stores of energy?

  1. Kinetic Energy
  2. Gravitational Potential Energy
  3. Elastic Potential Energy
  4. Chemical Energy