mass and spring?

Question

Ignoring U, and assuming Q=0

A spring has spring constant k=100N/m

a) Find displacement y produced by external force F=(-10)N.

b) Find total mechanical energy of mass+spring if oscillating with amplitude 10cm.

c) Find transfer by working for mass+spring when you move spring from 15cm to 5cm, assuming no change in kinetic energy.

I get:

a) (-0.1)m

b) 0.5J

c) (-1)J

I would just like some feedback on these answers thank you.

Answer 1

Agree with all answers.
A. f = kx ==> x = f/k = -0.1 m
B. At x = 0.1 m, PE = kx^2/2 = 0.5 J
C. At x = 0.15 m, PEi = kx^2/2 = 1.125 J
At x = 0.05 m, PEf = kx^2/2 = 0.125 J
Work done on spring = PEf-PEi = -1 J