In the gym, use an elastic band to strengthen your muscles. Suppose the gang
elastic behaves like an ideal spring with elastic constant K = 1 N / m. How much work
is it accomplished by extending the band by 50 cm?
A) 0.125 J
B) 0.25 J
C) 0.5 J
D) 1 J
E) 2 J
answer is A), how do you solve this one?