A spring with a constant of 66 kgs^-2kgs2 is lying on the ground with one end attached to a wall. An object with a mass of 33 kgkg and speed of 99 ms^-1ms1 collides with and compresses the spring until it stops moving. How much will the spring compress?

1 Answer
Mar 12, 2018

This is a case where kinetic energy E_k=1/2mv^2Ek=12mv2 is converted to spring potential energy E_(sp)=1/2kx^2Esp=12kx2.

E_k=1/2mv^2=1/2xx3xx9^2=121.5Ek=12mv2=12×3×92=121.5 JJ

Rearranging: x=sqrt((2E)/k)=sqrt((2xx121.5)/6)=6.36x=2Ek=2×121.56=6.36 mm

Explanation:

Here is the rearranging of the spring potential energy equation. I have left off the subscript for simplicity:

E=1/2kx^2E=12kx2

Multiply both sides by 2:

2E=kx^22E=kx2

Divide both sides by kk:

(2e)/k=x^22ek=x2

Swap the sides:

x^2=(2E)/kx2=2Ek

Take the square root of both sides:

x=sqrt((2E)/k)x=2Ek