A body weighing 500 g, thrown vertically upward with an initial speed of 40 m / s, rose to a height of 50 m.

A body weighing 500 g, thrown vertically upward with an initial speed of 40 m / s, rose to a height of 50 m. Determinant of the force of air resistance, considering it unchanged during the movement of the body.

Given:

m = 500 grams = 0.5 kilograms – weight of a body thrown vertically upwards;

g = 10 m / s ^ 2 – acceleration of gravity;

H = 50 meters – the height to which the body has risen;

v0 = 40 m / s – the initial speed with which the body was thrown upwards.

It is required to determine the force of air resistance Fс (Newton).

According to the law of conservation of energy, at the beginning of the throw, the body has only kinetic energy, and at the maximum height – only potential. The difference between the energies at the upper and lower points is the work to overcome the force of resistance, that is:

Eк = Ep + А

A = Ek – Ep = m * v0 ^ 2/2 – m * g * h = 0.5 * 40 ^ 2/2 – 0.5 * 10 * 50 =

= 400 – 250 = 150 Joules.

Then the resistance force is equal to:

Fc = A / H = 150/50 = 3 Newtons.

Answer: the force of air resistance acting on the body is equal to 3 Newtons.