A body with a mass of m = 20 kg falls from a height of H = 10 m without an initial velocity.

A body with a mass of m = 20 kg falls from a height of H = 10 m without an initial velocity. determine the kinetic and potential energy of the body at a height of h = 5m.

A body of mass m at rest at a height h1 has a potential energy Ep1 equal to

Ep1 = m * g * h1 = 20 * 10 * 10 = 2000 J.

In this case, since the body is at rest, then its velocity, and, accordingly, the kinetic energy are equal to zero:

Eк1 = 0.

The total mechanical energy of the body at this point is

E1 = Eк1 + Ep1 = 0 + 2000 = 2000 J.

When falling, part of the body’s potential energy is converted into kinetic energy. At a height of h2 = 5 m, the potential energy of the body Ep2 is equal to

Ep2 = m * g * h2 = 20 * 10 * 5 = 1000 J.

In accordance with the law of conservation of mechanical energy, the total mechanical energy in an isolated frame of reference is constant, therefore

E2 = E1 = 2000 J.

Then the kinetic energy of the body at a height of 5 m is

Eк2 = E2 – Eп2;

Eк2 = 2000 – 1000 = 1000 J.