Physics Homework Help

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>>380590
Here's my attempt at a solution. Since we're looking at the muzzle velocity, I'm assuming I should be using the mass of JUST the bullet, correct? You can see my answer is WAY off from what the back of the book tells me is correct.

>>380592
you're on the right-ish track
so the potential energy stored in the spring comes from the kinetic energy of the bullet
except it doesn't
it comes from the movement of the bullet & block
so you can find the speed of the bullet+block using that PE calculation
but can you find the speed of just the bullet from that?
source: I tried it, failed, then looked up the answer like a scrub :/

>>380590
you could ask on /sci/ too