(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

I've got a few physics homework questions I need a bit of help with. All relate to friction.

Here's the first one:

The µs = .2 between the boxes. Mass 2 (80kg) is on an air table. What minimum force will keep mass 1 (40kg) from slipping? What is the maximum acceleration that will keep the mass from slipping?

Here's a pic I drew up with FBDs.

2. Relevant equations

0.2Fn+Fsin30=mg or 0.2Fcos30+Fsin30=mg

3. The attempt at a solution

If I solve for F I get 582. 289N but the answer I was given is 637N. Where did I go wrong? or is that the right answer? I think it's because I didn't account for mass 2 moving when the force is applied but I'm not sure how to do that.

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Friction related problems

**Physics Forums | Science Articles, Homework Help, Discussion**