Why Is There a Difference Between Loss in GPE and Gain in EPE in Spring Energy?

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qazxsw11111
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A spring has an unstretched length of 0.650 and a weight of 0.400kg is attached and gently lowered till eqm point is reached. The spring is then stretched by a distance of 0.200m.

Loss in gpe=mgh=0.200x0.650x9.81=0.785 J
Gain in EPE=0.5 Fx= 0.5 x 0.400x 9.81 x 0.200=0.392 (?) Actually I don't really understand why this is so. But it is the answer.

Why are the two answers different?

Furthermore, if the spring is set into SHM with amplitude 0.200m, what is the resultant force at the lowest point of movement?
 
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qazxsw11111 said:
A spring has an unstretched length of 0.650 and a weight of 0.400kg is attached and gently lowered till eqm point is reached. The spring is then stretched by a distance of 0.200m.

Loss in gpe=mgh=0.200x9.81x9.81=0.785 J
Gain in EPE=0.5 Fx=0.392J

Why are the two answers different?

Furthermore, if the spring is set into SHM with amplitude 0.200m, what is the resultant force at the lowest point of movement?

in your gpe calc you use g twice and have no mass. Where Are you getting F for your epe? spell it out a little more for us.
 
Opps I typed too fast. I don't really understand why the EPE is so though...though I listed out the step according to answer scheme given. Anyone can help clarify?

Thanks.