Suppose that 2 J of work are needed to stretch a spring from its natural length of 30 cm to a length of 42 cm.

Question

 

How much work is needed to stretch it from 35 cm to 40 cm?

Answer 1

Work done,W1=2 J

Natural length,x1=30 cm=0.3 m

Stretched length,x2=42 cm=0.42 m

Recall the formulae:W=1/2*k*(x2^2-x1^2)

Plug into required values in above formula

2=1/2*k*(0.42^2-0.3^2)

k=46.296 N/m

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Natural length,x1=35 cm=0.35 m

Stretched length,x2=40 cm=0.4 m

Recall the formulae:W=1/2*k*(x2^2-x1^2)

Plug into required values in above formula

W=1/2*46.296*(0.4^2-0.35^2)

W=0.868 J