1 Work and energy
An electric motor lifts a mass of m=10 kg to a height of 5 m.
- Calculate the compressed work.
- How much energy is required if the efficiency of the motor is \(\eta = 80\%\)?
2 Potential energy in the reservoir
A reservoir contains \(2,000,000 m^3\) of water at a height of \(100 m\). Calculate the potential energy stored.
\( \rho = 1000\,\mathrm {kg/m^3}, g = 9{,}81\,\mathrm {m/s^2} \)
3 Kinetic energy of a car
A car with a mass of 1200 kg is travelling at 72 km/h. Calculate its kinetic energy.
4 Electrical energy of a device
A 2000 W kettle runs for 3 minutes.
- Calculate how much electrical energy it has consumed.
- How much energy is needed to heat 5 litres of water from 20 °C to 100 °C?
5 Energy and power
A heating device has a power consumption of P = 2 kW and is operated for t = 3 hours.
- How much energy is consumed?
- If the electricity price is €0.30/kWh, how much will it cost?
6 Efficiency
A generator produces an electrical power of \(P_{\text {el}}\) = 1 kW by absorbing a mechanical power of \(P_{\text {mech}}\) = 1.5 kW.
- Calculate the efficiency
- How large must \(P_{\text {mech}}\) be to generate \(P_{\text {el}}\) = 2 kW?
