my physics work is not ok.

i got these questions for my homework and they're ones where you have to use multiple equations, i tried some of them but they went terribly wrong so,,
help please??

How much energy does a spring store when its constant is 4N/m and it is compressed by 6cm?
If this spring is released and pushes a 0.1kg marble along a track, what speed will the marble reach?
If a child of mass 40kg jumps onto a trampoline of spring constant 200N/m from a height of 2m, how far will the elastic stretch?
If a moose of mass 300kg jumps vertically with an initial speed of 5m/s. How high will it reach?

What have you tried for the first one? Do you know the equation for energy stored by a spring?

i know elastic potential,
0.5ke²
0.5x200x2²
= 400J

after that it just got a bit confusing, i tried re-arranging gpe

The equation you're using is right, but you should check the numbers you're substituting in. Where are you getting the 200 and 2 from?

i was looking at the wrong question lmao,

for question 1 i got:
0.5ke²
0.5x4x0.06²
= 0.0072J

i didn't know what to do after that /:

That's right.

In the second part is spring is released, so it's going to go back to its normal normal length. This means its extension is 0 so it now stores no energy. We know that energy can't be created or destroyed, so what happens to its energy when it does this? What form does it go to?

doesn't it transfer to kinetic energy? and then you re-arrange the kinetic energy equation to find velocity?

Yep, that's it. You have the kinetic energy of the marble and its mass, so you can rearrange the kinetic energy equation to get the velocity. Have a go at doing that.