Question

A spring of length of 5cm is stretched to 7.5cm when a mass of 2500g is hung on it. What force must be hung on the spring for it to have an extension of 5cm

Answer 1

Answer

In case of spring

Restoring force is equal to the it's weight due to gravity.

$F=Mg=kx$

$k=\frac{Mg}{x}=\frac{2.5\times9.8}{0.025}=980$ N/m

Now in second case required force is calculated as

$F'=980\times0.05=49N$