A person weighing 70 kg is in an elevator, the speed of which is directed downward and is equal to 1.2 m / s

A person weighing 70 kg is in an elevator, the speed of which is directed downward and is equal to 1.2 m / s. the acceleration of the elevator is directed upwards and is equal to 2m / s ^ 2. determine the weight of the person.

m = 70 kg.

g = 9.8 m / s ^ 2.

V = 1.2 m / s.

a = 2 m / s ^ 2.

P -?

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

We write 2 Newton’s law in vector form: m * a = N + m * g, where m is the mass of a person, a is the acceleration of motion, N is the force with which the floor presses on a person, m * g is the force of gravity that acts on person.

Let’s write 2 Newton’s law for projections on the vertical axis, which is directed vertically upward: m * a = N – m * g.

The force with which the floor presses on a person will be determined by the formula: N = m * (a + g).

According to Newton’s 3 law: N = R.

P = m * (a + g).

P = 70 kg * (2 m / s ^ 2 + 9.8 m / s ^ 2) = 826 N.

Answer: the weight of a person is P = 826 N.