A 75 Kg Petty Thief

Yous are hither

Question:

A 75-kg fiddling thief wants to escape from a third-story jail window. Unfortunately, a makeshift rope made of sheets tied together can back up a mass of but 58 kg. How might the thief use this "rope" to escape? Give a quantitative answer.

Giancoli, Douglas C., Physics: Principles with Applications, 7th Ed., ©2014. Reprinted by permission of Pearson Education Inc., New York.
The question volition exist visible after logging in, every bit required by Pearson Education Inc.

Giancoli seventh Edition, Chapter iv, Problem xiii

(1:38)

Transcript for this Giancoli solution

This is Giancoli Answers with Mr. Dychko. If the thief doesn't quite apply his full weight to the canvas then the sheet won't break merely this volition involve having the thief accelerate down because the force that he applies to the canvass and therefore the force the sheet applies to him considering those are Newton'south third police pairs volition not exist equal to his weight. And so, the maximum force that the thief can expect from the sheets is 58 kilograms times nine.eight Newtons per kilogram which is 568.4 Newtons. So, nosotros'll discover the slowest acceleration downwards by saying, allow'due south assume he's expecting the maximum force from the sheets forcefulness of gravity downwards on the thief is 75 kilograms times 98 Newtons per kilogram which is 735 Newtons and so, the internet force is mass times acceleration. And so, the force of the sheet upward minus the strength of gravity on the thief downwardly is ma, and we'll carve up both sides by m. And now we notice the acceleration that will be needed so that he doesn't break the sheets. And so, we have the sail force up minus gravity downward divided past 75 kilograms gives negative 2.two m/s squared, and the thief could accelerate faster than that past having a smaller force expected from the sheet which would make this difference greater and, acceleration greater. But this is the minimum dispatch down to avoid breaking the canvas.