A load weighing 120 kg with the help of a rope is uniformly accelerated downward and travels

A load weighing 120 kg with the help of a rope is uniformly accelerated downward and travels a path of 72 m in 12 seconds. Determine the weight of the load?

m = 120 kg.

g = 10 m / s2.

S = 72 m.

t = 12 s.

R – ?

The weight of the load P is the force with which it presses on the support or stretches the suspension.

Two forces act on the load: gravity Ft directed vertically downward, N – rope tension force directed vertically upward.

m * a = m * g + N – 2 Newton’s law in vector form.

For projections onto the vertical axis of the OU, which is directed vertically upward, 2 Newton’s law will take the form: – m * a = – Fт + N.

N = Fт – m * a.

The force of gravity Ft is determined by the formula: Ft = m * g.

N = m * g – m * a = m * (g – a).

We express the acceleration a by the formula: a = 2 * S / t ^ 2.

N = m * (g – 2 * S / t ^ 2).

According to Newton’s 3 laws, the force P, with which the body pulls the rope, is equal to the force N, with which the rope pulls the body: P = N.

P = m * (g – 2 * S / t ^ 2).

P = 120 kg * (10 m / s2 – 2 * 72 m / (12 s) ^ 2) = 1080 N.

Answer: when lowering, the body weight is P = 1080 N.