Question

A force of 10lb is required to hold a spring stretched 4 in beyond its natural length. How much work is done in stretching it from its natural length to 6 in. beyond its natural length

so hookies law states

f(x) = kx
so I have
10lbs = k(4in)
k = 10/4

so I have

f(x) = (10/4)(6) = 15lbs-in

My text book states the answer as

15/4 ft-lb

where did I got wrong?

Answer 1

U have calculated k right

However, ur question asks for the WORK done and not the force. Work = k * x^2

Answer 2

so force is

f(x) = k*x
and
work is
f(x) = k*x^(2)

Answer 3

yes

Answer 4

thanks for clarifying