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mv squared divided by 2=mgh (make v the subject ?)
This is for my boy ,If anyone can help could they include the workings out ty in advance

--- Post Update ---

This is what I got ,but not sure if I did it right
The masses cancel out on both sides.
You're left with:
gh = 1/2v^2
multiply both sides by 2 and you end up with:
2gh = v^2
take the square root of both sides and you have:

v = the square root of 2gh