A brick weighing 400 g freely falls from a height of 0.9 m. Determine the kinetic and potential energy

A brick weighing 400 g freely falls from a height of 0.9 m. Determine the kinetic and potential energy of the stone at the height at which its speed will be equal to 4 m / s.

h1 = 0.9 m.

m = 400 g = 0.4 kg.

g = 10 m / s2.

V1 = 4 m / s.

V0 = 0 m / s.

Ek1 -?

En1 -?

The kinetic energy of the body Ek is determined by the formula: Ek = m * V2 / 2.

Ek1 = 0.4 kg * (4 m / s) ^ 2/2 = 3.2 J.

Since the air resistance in this problem can be neglected, the law of conservation of total mechanical energy is valid for the body: Ek0 + En0 = Ek1 + En1.

Since the body falls freely, Ek0 = 0 m / s.

The potential energy of the body En is determined by the formula: En = m * g * h.

m * g * h = Ek1 + En1.

En1 = m * g * h – Ek1.

Ep1 = 0.4 kg * 10 m / s2 * 0.9 m – 3.2 J = 3.6 J – 3.2 J = 0.4 J.

Answer: Ek1 = 3.2 J, En1 = 0.4 J.