Answer:
= 4 joules
Explanation:
Work done by a spring is given by the formula;
Work done = ke²
Where, k is the spring constant
e is the extension.
But;
k = F/e
= 5 N/0.1 m
= 50 N/m
Therefore;
Work done when the extension is 0.4 m, will be;
Work done = 1/2 × 50 × 0.4²
= 4 joules