# Day 63: More comfortable each day + a great challenge problem

**Posted:**December 2, 2012

**Filed under:**School Days Leave a comment

Today we did more practice utilizing Newton’s laws to solve problems. Students are getting confident, which is a lot of fun. I had a couple of students solve this one (different than the work above, basic question below), which requires successful use of both N2 and N3, nice work! Note: the problem asks to find the value of the max force F to apply to the upper block such that they don’t slip apart while accelerating. A good extension is to ask the same question with F on the lower block, then ask which F is bigger. It’s a pretty elegant solution.