The force an ideal spring exerts on an object is given by F_x = −kx, where x measures the displacement of the object from its equilibrium (x = 0) position. If k = 60 N/m, how much work is done by this force as the object moves from x = −0.20 m to x = 0? A) −1.2 J B) +1.2 J C) +2.4 J D) −2.4 J E) +3.6 J

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Quizplus · Accepted Answer

We can use the formula for work done by a variable force: W = 1/2 kx2(final)-1/2 kx2(initial). Plugging in the values, we get W = 1/2 (60 N/m)(0 m)2 - 1/2(60 N/m)(-0.20 m)2 = +1.2 J. The positive sign indicates that work is done on the object by the spring force. Therefore, the correct answer is choice B.

The Force an Ideal Spring Exerts on an Object Is