A car weighing 35 tons moves on the wall at a speed of 0.2 m / s. When the car is fully braked, the buffer

A car weighing 35 tons moves on the wall at a speed of 0.2 m / s. When the car is fully braked, the buffer springs are compressed by 12 cm. Determine the maximum compression force of the springs and the duration of braking.

Given:
m = 35t = 35000kg,
v1 = 0.2m / s,
v2 = 0,
s = 12cm = 0.12m;
To find
F and t;
The compression force of the spring can be found from the law of conservation of energy:
Work on compression of a spring with a stiffness k
A = (k * s ^ 2) / 2 = F * s / 2
is equal to the change in the kinetic energy of the car:
W = (m * v ^ 2) / 2;
F = (m * v ^ 2) / s = 35000 * 0.04 / 0.12 = 11667H;
The momentum of the force is equal to the change in the momentum of the car. Since the force grows linearly from 0 to the maximum value of F, you need to take half of this value:
F * t = m * (v1 – v2) = m * v1;
t = m * v1 / F = 0.6s.