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Audio Video Interleaved Video  |  2012-12-18  |  5.7 MB  |  500x500  |  1fps  |  3 minutes, 48 seconds
Transcription: In this example, a construction worker is pushing a rock whose mass is 300 kilograms. We know that the worker is exerting a force of 400 newtons. It's directed to the north because he wants the rock to accelerate to the north. We also know there's a frictional force. That frictional force opposes motion, so even though we don't know the size of the frictional force, we know it's oriented to the south. There's one more thing we know. We know that the rock is accelerating with an acceleration of 0. 0.12 meters per second squared north. Okay, those are all the things we know. What we need to do i ...