equations/formulas

equations/formulas

1. electricity

   • power = voltage x current
   • voltage = current x resistance
   • charge = current x time
   • energy = voltage x charge
   • energy = voltage x current x time.
   • Total cost = number of units x cost per unit

2. energy

   • Efficiency (%) = (useful energy out ÷ total energy in) x 100.
   • GPE = mass x gravity x height.
   • Kinetic Energy = 0·5 x mass x velocity2
   • work done = force x distance
   • work done = energy transferred.
   • power = energy ÷ time.

3. forces and motion

   • speed = distance ÷ time
   • acceleration = change in velocity ÷ time.
   • Force = mass x acceleration
   • weight = mass x gravity
   • momentum = mass x velocity
   • change in momentum = Force x time
   • density = mass ÷ volume
   • pressure = force ÷ area
   • velocity = displacement / time