Question

A spring 20cm long is stretched to 25cm by a load of 50N.what will be its length when stretched by 100N assuming that the elastic limit is not reached?

Answer 1

According to Hooke's law, the elongation is directly proportional to the force that stretches a spring:

$$x=F/k.$$

Find the spring constant:

$$k=F_1/x_1=50/25=2\text{ N/cm}.$$

Find the length under 100 N:

$$x_2=F_2/k=100/2=50\text{ cm}.$$