Here is a link to the pulley diagram: http://img287.imageshack.us/img287/2904/1711082ao.gif [Broken] (a) What is the largest value the force F may have so that m2 remains at rest on the floor? I said 20N here (which is wrong) because if m2 is on the floor, there will be a downward force on the pulley of 20N. If that was matched by an upward force of 20N it would cancel out. (b) What is the tension in the string if the upward force F is 100 N? This would mean that both masses are off the ground. Because of this (relative to the pulley), mass m1 would be accerating upwards at 10 m/s2. I got this by saying -10N + 20N = 10N, then dividing it by one kilogram. However, this is also incorrect. (c) With the tension determined in part (b), what is the acceleration of m1? Here I said that the acceleration would be the 10 m/s2 found in part (b) plus 100N/3kg=33.3...m/s2, for a total upwards acceleration of 43.3 m/s2. All of my answers were incorrect and I cannot see why. Does anyone see my errors? Thank you.