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Picture: http://session.masteringphysics.com/problemAsset/1000077659/2/knight_Figure_10_69.jpg

We also know:

a) What is the maximum compression of the spring? 2.36m I got this answer correct

My question is on b:

At what compression of the spring does the box have its maximum speed?

I was thinking this was a trick question. From the picture, the moment the box hits the spring, it slows down because the kinetic energy is transferred to spring potential energy. So i initially thought that the speed would be maximum right before it touches the spring. Therefore, compression of the spring would be at 0m.

That was incorrect.

Then I was thinking, maybe i was wrong and that maybe maximum velocity would be when acceleration is = 0.

To find the point when acceleration would be 0, i used:

(4m x 9.8m/s^2 x 17kg x sin(30)) = 333.2 N for work done while sliding down before hitting the spring

And we know F = kx

I was thinking that acceleration would equal 0 when kx = 333.2N because the compression would counteract the sliding down force.

With k = 190 i get x to get 1.75m

That was also incorrect

I have like 2 tries left on this stupid program.

Please someone help me out.