To stop a body weighing 0.4 kg, moving at a speed of 5 m / s in a horizontal direction, use a spring.

To stop a body weighing 0.4 kg, moving at a speed of 5 m / s in a horizontal direction, use a spring. Find the stiffness of the spring so that when the body is fully stopped, the spring is compressed by 10 cm.

Decision:
The kinetic energy of the moving body is converted here into the compression energy of the spring.
0.5mV ^ 2 = 0.5kx ^ 2
Reduce by 0.5:
mV ^ 2 = kx ^ 2;
0.4 * 25 = k 0.1 ^ 2 = k * 0.01;
10 = 0.01k;
k = 10 / 0.1 = 1000;
Answer: k = 1000.