Joule - Practical Examples

Practical Examples

One joule in everyday life is approximately:

• the energy required to lift a small apple one metre straight up. (A mass of about 102 g = 1⁄_9.81 kg)
• the energy released when that same apple falls one metre to the ground.
• the energy delivered by a 1 watt solar panel every second.
• the energy released as heat by a person at rest, every 1/60th of a second.
• the kinetic energy of a 50 kg human moving very slowly (0.2 m/s).
• the kinetic energy of a tennis ball moving at 23 km/h (14 mph).

Since the joule is also a Watt-second and the common unit for electricity sales to homes is the kWh (kilo-Watt-hour), a kWh is thus 1000 (kilo) x 3600 seconds = 3.6 MJ (Megajoules).