1. The problem statement, all variables and given/known data A block is placed against the vertical front of a cart. The coefficient of static frction between the block and the cart is [itex]\mu[/itex]s. What acceleration must the cart have in order that the block does not fall? How would an observer on the cart describe the behavior of the block? 2. Relevant equations F=[itex]\mu[/itex]s*n F=ma 3. The attempt at a solution I have no idea how to start this problem. I know that the force pushing up on the block is equal to mg. I tried drawing acceleration as a horizontal vector, then setting a=mg, then trying to solve, but that didn't quite work out..