If I apply the Work-Kinetic Energy theorem to a situation in which an object is lifted or lowered then I can form the equation K(f)-K(i)=W(net)=W(applied)+W(gravity)(adsbygoogle = window.adsbygoogle || []).push({});

This equation shows that if K(f)=K(i) then the above equation reduces to:

W(applied)= -W(gravity)

Now in the situation in which a force is applied to an object attached to a spring we can form a similar equation:

K(f)-K(i)=W(applied)+W(spring)

Now my textbook says that this equation reduces to W(applied)= -W(spring) if and only if the object to which the force was applied to is stationary before and after the displacement.

Why is this so.If the object has some value K(i)>0 at the start of the displacement and at the end of the displacement this value is the same ie. K(f)=K(i), then surely the work done by the applied force to maintain the kinetic energy must be equal in magnitude and opposite in sign to the work done by the spring.

Am I missing something here?I don't see how my reasoning is incorrect.

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# Homework Help: Work-Kinetic Energy Theorem applied to a Spring Force

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