I'm trying to improve on tension problems so I am practicing using this website: http://www.education.com/study-help/article/tension/ I am on problem 6, but I keep coming up with the wrong answers. I attempted this by trying to show the net forces for each box. Box M net forces T upwards Mg downwards F = T - Mg = Ma Box 2M net forces T upwards T' downwards ***should I include the weight (2Mg) of this box??? Box 4M net forces 4Mg downwards T' upwards F = 4Mg - T' = 4Ma I have a feeling there is an error in box 2M that is fudging with my results. Lastly, does T = 6Mg? Help??
yes always include the weight in any free body diagram yes yes, correct your error for the net forces acting in the FBD of the 2M block.
I solved it and it still incorrect. Block M T - mg = ma <---plug in m = 1 Kg T - 9.8 = a T = 9.8 + a equation 1 Block 2M T' + 2mg - T = 2ma <---Plug in m = 1 kg T' + 2(9.8) - T = 2a T' + 19.6 - T = 2a equation 2 Block 4M 4mg - T' = 4ma < --- plug in m = 1 kg 4(9.8) - T' = 4a T' = 39.2 - 4a equation 3 Substitute equation 1 and equation 3 into equation 2 equation 2: T' + 19.6 - T = 2a (39.2 - 4a) + 19.6 - (9.8 + a) = 2a Solve for a. a = 7 m/s^2 Correction answer is 8.6 m/s^2.
We were correct :D The answer provided is incorrect I believe. Someone solved it out and got the same answer as I did here, http://www.myteacherpages.com/webpages/niedzielam/files/AP Review 01 Tension SOLUTIONS.pdf.