1. The problem statement, all variables and given/known data A string is attached on a pulley, with Mass 1 (2 kg) hanging from the left and Mass 2 (5 kg) hanging from the right. The pulley itself is being pulled upwards with a force of 100N. Find the tension T in the string, and the accelerations of both masses. We consider the pulley and string to be massless, and no friction. Gravitational acceleration is g=9.8 m/s^2 F = 100N m1 = 2kg m2 = 5kg a1 = acceleration of Mass 1 a2 = acceleration of Mass 2 a = acceleration of the whole system T = tension in the string 2. Relevant equations m1 a1 = T - m1 g m2 a2 = T - m2 g 3. The attempt at a solution First I found the acceleration of the system: the total force on the system is F - (m1+m2)g (because gravity pulls it downwards). So a = F/(m1+m2) - g. Since the string is not extendable, the relative accelerations of the masses with respect to the pulley are equal in magnitude and with opposite signs: a1 - a = -(a2 - a) a2 = 2a - a1 = 2F/(m1+m2) - 2g - a1 Replacing a2 in the Relevant equations: m1 a1 = T - m1 g m2 [2F/(m1+m2) - 2g - a1] = T - m2 g After solving this system for T (by multiplying the second equation by m1/m2 and adding both equations to eliminate the a1 term), I get: T = 2m1m2F/(m1+m2)^2 = 2000/49 = 40.82 N But the answer is supposed to be 50N. And the accelerations I get are also not the same as in the answers. Where did I go wrong?