The first part of this problem says that a 8.0kg stone rests on top of a spring, and compresses it by 10.0cm. It then asks what the spring constant is. This is the work I did (assuming g = 10m/s^2, not 9.8m/s^2): (8.0kg)(10m/s^2) = 1/2k(10cm)^2; 80N = 50cm; k = 1.6 But, the textbook says the answer is .8. I don't understand why it's half my answer. Any help would be greatly appreciated.