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deliciousiron

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## Homework Statement

"a metal wire of diameter .23mm and unstretched length 1.405 is suspended vertically from a fixed point. when a 40n weight was suspended from the lower end of the wire, the wire stretched by an extension of 10.5mm. calculate the work done on the spring."i know the formula for work done on a spring, but i do not understand why it's given by half of the force. the 40n's force is constant, so why do i need to half it?

why isn't it just force*distance/40*(10.5*10^-3)??