The concrete slab has a mass of 1 ton. what will be its weight if a) the plate is lifted vertically with

The concrete slab has a mass of 1 ton. what will be its weight if a) the plate is lifted vertically with an acceleration of 0.2 m / s2 with the help of a crane; b) it moves uniformly; c) it descends with an acceleration; d) falls freely.

m = 1 t = 1000 kg.

g = 9.8 m / s2.

a = 0.2 m / s2.

P -?

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

Let’s write Newton’s 2 law for a plate in vector form: m * a = m * g + N, where m is the mass of the plate a is the acceleration of the plate, m * g is the force of gravity, N is the pulling force of the cable.

1) Acceleration of the plate a directed vertically upwards. m * a = – m * g + N.

N = m * a + m * g = m * (a + g).

According to Newton’s 3 law: N = P.

P = m * (a + g).

P = 1000 kg * (0.2 m / s2 + 9.8 m / s2) = 10000 N.

2) The plate is lifted evenly, the acceleration of the plate is a = 0.

0 = – m * g + N.

N = m * g.

According to Newton’s 3 law: N = P.

P = m * g.

P = 1000 kg * 9.8 m / s2) = 9800 N.

3) Acceleration of the plate and directed vertically downward: – m * a = – m * g + N.

N = m * g – m * a = m * (g – a).

According to Newton’s 3 law: N = P.

P = m * (g – a).

P = 1000 kg * (9.8 m / s2 – 0.2 m / s2) = 9600 N.

4) The plate falls freely: m * a = m * g.

There is no slab weight, it is in a weightless state.

P = 0.