Hi everyone, wondering if anyone can help me with this little problem... An object with mass m1 , resting on a frictionless horizontal table, is connected to a cable that passes over a pulley and then is fastened to a hanging object with mass m2. Find the acceleration of each object and the tension in the cable. For this coordinate system, where the x-axis is pointing to the right, which is the positive, and the y-axis is pointing downwards, which is positive: http://www.imagehosting.com/show.php/1011793_Coordinate.bmp.html Given that T is the tension, the equations should be: m1*(a) = T; m2*(a) = -T + m2*(g); However, if i switch the x-axis from pointing rightwards to pointing leftwards, i will get this: http://www.imagehosting.com/show.php/1011808_Coordinate1.bmp.html The equations become: m1*(a) = -T; m2*(a) = -T + m2*(g); I am confused as to how to solve this using the 2nd coordinate system, as i feel that coordinates should not affect the answer. My question is that what is it that is wrong in my equations that i cannot get the answer? Or is it possible that this assumption is flawed? I feel that maybe the tension have to opposite each other (having opposite signs) regardless of coordinates, but i am not very sure. Thanks to all for your time.