Question

a slingshot has 12 J of elastic potential energy when it screeched  to 0.2 m away from its equilibrium. What is the spring constant for the slingshot

Answer 1

$$PE=\dfrac{1}{2}kx^2,$$ $$k=\dfrac{2PE}{x^2}=\dfrac{2\cdot12\ J}{(0.2\ m)^2}=600\ \dfrac{N}{m}.$$