Posted by tom on .
A 3.2 kg block is hanging stationary from the end of a vertical spring that is attached to the ceiling. The elastic potential energy of this spring/mass sytem is 2.1 J. What is the elastic potential energy of the system when the 3.2 kg block is replaced by a 5.3 kg block?

honors physics 
bobpursley,
find k for the initial block.
Weight= kx when
2.1J=1/2 kx^2 or
mg=kx and
4.2J=kx^2 or
4.2=mg*x solve for x
know, knowing x, solve for k.
replace the mass, find new x.
PE= 1/2 k (newx)^2