In case you were curious about the previous two problems but didn't exactly know where to start, here are a few tips:
- Start with the law of cosines. You need it for the distance between the two planes. Take the derivative of the law of cosines with respect to time. You want to know da/dt (a being the distance between the two planes).
- First find theta one and theta two. You need to find the net force on the system, which would be the force of m2 minus the force of m1. You might want to draw a free body diagram for each mass, and don't forget friction. You'll need the formula for friction, and a few Newtonian mechanics equations. Good luck!