What mass should a body have so that at a height of 20 m its potential energy equals 800 J?

h = 20 m;

Ep = 800 J;

g = 9.8 N / kg;

m -?

The potential energy is calculated by the formula: En = mgh, where m is the mass of the body, g is the acceleration of gravity (constant equal to 9.8 N / kg), h is the height. Let us express the mass from this formula: m = Ep / gh.

Substitute the known values into the resulting formula and calculate.

We get: m = 800 J / (9.8 N / kg * 20 m) ≈ 4.1 kg.

Answer: the body must have a mass of ≈ 4.1 kg.