Question

Niagara falls are 50m high. calculate the potential energy of 0.1 cubic meter of water at the top relative to the bottom. density of water is 1000 kg m^-3. take g= 10m/s^2

Answer 1

Potential energy is:

$$E=mgh$$

Mass:

$$m=\rho*V$$

then:

$$E=\rho Vgh=1000\times 0.1\times 10 \times 50 = 50000 J = 50 kJ$$