Alright so I'm in AP Physics B, senior in HS. We've just started on forces and I was gone from a couple class periods and I'm just not getting how to work these problems. They seem easy enough when I read them, but then when I try to put it on paper I just get stumped. So I have a couple problems on my homework that if anyone would be able to tell me how to set it up and what not--I'd really appreciate it.(adsbygoogle = window.adsbygoogle || []).push({});

1

A student presses a book between his hands. The forces that he exerts on the front and back covers of the book are perpendicular to the book and are horizontal. The book weighs 31 N. The coefficient of static friction between his hands and the book is 0.40. To keep the book from falling, what is the magnitude of the minimum pressing force that each hand must exert?

2

The speed of a bobsled is increasing, because it has an acceleration of 2.4 m/s/s. At a given instant in time, the forces resisting the motion, including kinetic friction and air resistance, total 450 N. The mass of the bobsled and its riders is 270 kg. (a) What is the magnitude of the force propelling the bobsled forward? (b) What is the magnitude of the net force that acts on the bobsled?

Alright so those are two of the many problems I've been assigned to do, but the others are a lot like these. If you could just tell me how I would go about solving it or setting it up--just pointing me in the right direction, I'd really appreciate it. If you want to solve it go ahead, an example wouldn't hurt ;) --but by no means am I asking you to do this for me.

Thanks.

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# Homework Help: Figuring forces (need some help)

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