How much force is needed to stretch a spring 1.2 m if the spring constant is 8.5 N/m?

Use Hooke’s law, F = kx, where k is the spring constant and x is the stretch. Substituting k = 8.5 N/m and x = 1.2 m gives F = 8.5 × 1.2 = 10.2 N. Therefore, the force needed is 10.2 N, choice D.

AI-written and checked against the verified answer.