1. The problem statement, all variables and given/known data Suppose that in the figure shown in the URL below, the masses of the blocks are M = 2.6 kg and m = 6.6 kg. What are (a) the magnitude of the acceleration and (b) the tension in the cord? http://www.google.com/imgres?num=10...5&start=0&ndsp=21&ved=0CHkQrQMwDQ&tx=48&ty=63 2. Relevant equations F= ma 3. The attempt at a solution I found the Fnet, y and Fnet, x for the hanging block (H) and for the sliding block (S). For S Fnet, y = May which becomes FN = FgS, and Fnet becomes T= Ma For H Fnet, y becomes T-FgH = may, which becomes T-mg= -ma I combined the two equations to cancel out T and solve for acceleration. T-mg+ma = T- Ma -mg+ma = - Ma -mg+ma+Ma = 0 ma+Ma = mg a(m+M) = mg a = mg/(m+M) That gave me the correct answer for (a) but when I went to try to cancel out a and solve for tension T = Ma, T-mg = -ma a = T/M a= (T-mg)/(-m) a-T/M = a-(T-mg)/(-m) -T/M = -(T-mg)/(-m) (T-mg)/(-m) - (T/M) = 0 M(T-mg)/(-m) - (-m)(T)/M = 0 MT-Mmg/(m+M) -mT/(m+M) = 0 T((M-mg)-m)/(m+M) = 0 T= -M+mg +m/(m+M) That gives a negative number for tension. What did I do wrong?