A load suspended on a spring with a stiffness of 400 N / m led to its elongation by 4 cm. What is the weight of the load?

Let’s start with a formula, which will allow us to express mass from it, knowing the stiffness and elongation – the formula for the elastic force. F = k * l. You need to use another force formula to express the mass from there. F = m * g. We express m: m = F / g. We substitute instead of F its value from the elastic force formula: m = k * l / g. But first, let’s translate the length into the SI system. 4 cm – 0.04 m.Now we substitute and calculate: m = 400 * 0.04 / 10 = 16/10 = 1.6 kg.