Question

A force of 18 lb is required to hold a spring stretched 8 in. beyond its natural length. How much work W is done in stretching it from its natural length to 10 in. beyond its natural length

Answer 1

Answer: 18.75 lb.ft

Explanation:

Given

Force required to stretch spring 8 in. is 18 lb

it can be written

`\Rightarrow F=kx\\\Rightarrow 18=k(8)\\\\\Rightarrow k=(18)/(8)=(9)/(2)\ lb/in.`

Work done in stretching from its natural length to 10 in.

`\Rightarrow W=(1)/(2)kx^2\\\\\Rightarrow W=0.5* (9)/(2)* (10)^2\\\\\Rightarrow W=225\ lb.in.\ or\\\Rightarrow W=18.75\ lb.ft`