1. The problem statement, all variables and given/known data A 10kg block is resting on a 5kg bracket, which rests on a frictionless surface. The coef. of static and kinetic friction between the block and bracket are .4 and .3, respectively. Find out a) the max force that can be applied to the block without the block sliding on the bracket and b) the acceleration of the 5kg bracket. http://img114.imageshack.us/img114/1958/56qe9.jpg [Broken] 2. Relevant equations Fnet = m * a 3. The attempt at a solution This seems like a very simple question but I'm just having an issue with it (plus the book calls it a "challenging" problem so it just seems too easy). Finding a) was pretty simple, just do 10 * .4 * 9.81 (Normal Force * [tex]\mu[/tex]k). I came up with 39.24N as the answer. To find b I thought it would just have to apply newton's second law. 39.24N = (5kg + 10kg) * a a = 2.62m/s But since this seemed too easy so I thought that I was wrong. Since the bracket exerts a frictional force on the block, do I have to include the force of the block on the bracket as given by newton's third law? That seemed logical to me but then it would obviously negate the force of the string which would mean no acceleration, and it seems extremely obvious that there would be acceleration. Any help would be great, thanks.