physics
posted by Kyle .
a force of 10 N holds an ideal spring with a 20N/m spring constant in compression. The potential energy stored in the spring is..? 0.5J, 2.5J, 5.0J, 10J, or 200J?
POtential energy? Wouldn't it be 1/2 kx^2,
but x= F/k, so 1/2 kx^2= 1/2 k*F^2/k^2 and that can be reduced.

A 0.5kg block attached to an ideal spring with a spring constant of 65N/m oscillates on a
horizontal frictionless surface. The total mechanical energy is 0.79 J. What is the greatest extension
of the spring from its equilibrium length? 
square root of(.79/(.5*65))

a. PE = 1/2 * kx^2.
or d = 10 * 1m/20N = 0.5 m.
PE = 0.5*F*d = 0.5 * 10 * 0.5 = 2.5 J.