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blessedcurse
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Homework Statement
The amount of WORK to stretch a spring 4 feet beyond its natural length of 2 feet is 10 ft-lbs. Find the work required to stretch the spring from 4 feet to 7 feet.
Homework Equations
W=[tex]\int^{b}_{a}Fdx=\int^{b}_{a}kxdx=[kx^{2}/2]^{b}_{a}[/tex]
The Attempt at a Solution
10=[tex][kx^{2}/2]^{4}_{0}[/tex]
10=k(16)/2-k(0)/2
10=8k
k=4/5
W=[tex][kx^{2}/2]^{b}_{a}[/tex]
W=4/5[tex][x^{2}/2]^{5}_{2}[/tex]
W=4(25)/10-4(4)/10
W=42/5
W=8.4 ft*lb
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