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.