A box of mass 4.0 kg is accelerated from rest by a force across a floor at a rate of $2.0 \textrm{ m/s}^2$ for 7.0 s. Find the net work done on the box.

VIDEO TRANSCRIPT

This is Giancoli Answers with Mr. Dychko. The net work done on the box is the net force applied multiplied by the distance. Of course, these have to be parallel and so on, which they are in this case. And the net force is mass times acceleration and the distance, we can write as, one-half times acceleration times time squared based on our kinematics formula assuming that it starts from rest, which I believe it does. Yeah, it says, "accelerated from rest" so that's good. So we substitute both of those into our work net formula so Fnet is ma, which we write here. And d is one-half a t squared, which we write there. And that makes a squared times t squared times m over 2. So we plug in numbers and there we go. We have 4.0 kilograms times 2 meters per second squared acceleration squared times 7 seconds squared divided by 2, which is 390 joules, is the net work done on the box.