Barron's 2nd Edition DT Q23

Barron's Book

23) We need to find the acceleration of mass m[2]. It is important to realize that m[1] and m[2] will accelerate at the same speed. The system as a whole accelerates together. So, we can also use net force to solve for the net acceleration.

Where F is force, m is mass, and a is acceleration

The net force will be 12 because the other forces(weight and normal force) will cancel out. our total mass will simply be the sum of m[1] and m[2]. After plugging these values in, we can solve for the net acceleration, our answer.

Where F is force, m is mass, and a is acceleration

Answer: C