Question

Hello,

I hope you are having a good day.

Please confirm the work I did is correct. I need to better understand how exactly to calculate moment using the internal forces.

I don't understand why the moment did not return to zero at the point 4.5 m from the beginning. I'm used to the moment beginning at zero and ending at zero,

at the last force. This is a cantilever beam; maybe that is why???

Please let me know if my work is correct. If not, how exactly is the moment calculated in this situation.  Your instructions on figuring out moments is more important than the answers; I really don't need the answers; I made this problem up to learn about figuring out moments.

11-5 te huM Im

Thanks!

Answer 1

Sigma F_y = 0 V_A = (80 times 3) + 60 = 300 KN Sigma F_x = 0 Rightarrow H_A = 0 M_x = -60(x - 1.5) - 80(x - 3) (x - 3)/2 = -60(x - 1.5) - 80/2(x - 3)^2 M_x = 0 = 0 M_x = 1.5 = 0 M_x = 3 = -60(3 - 1.5) = -90 KN - M M_x = 6 = -60(4.5) - 80(3.0)^2/2 = -270 - 360 = -530 KN - m