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The uniform 71-lb log is supported by the two cables and used as a battering ram

ID: 1828334 • Letter: T

Question

The uniform 71-lb log is supported by the two cables and used as a battering ram. If the log is released from rest in the position shown, calculate the initial tension induced in each cable immediately after release and the corresponding angular acceleration ? of the cables.


For the anglur acceleration I got 6.4188 rad/s^2 is this correct? If not, please help me calculate the correct number as well as the Ta and Tb in pounds.


Here is a link to the question/diagram and answer format:

http://i1334.photobucket.com/albums/w655/salonemark/6-19_zps4b708227.jpg

The uniform 71-lb log is supported by the two cables and used as a battering ram. If the log is released from rest in the position shown, calculate the initial tension induced in each cable immediately after release and the corresponding angular acceleration ? of the cables. For the angular acceleration I got 6.4188 rad/s^2 is this correct? If not, please help me calculate the correct number as well as the Ta and Tb in pounds.

Explanation / Answer

This is a curvilinear translation problem.

a - Angular acceleration

a_t - Tangential acceleration

a_n - Normal acceleration = 0

Sum forces in the normal direction: Ta + Tb - 71cos22 = 0

Ta + Tb = 71cos22 (eq1)

Sum forces in tangential direction: 71cos68 = (71/32.2)*(a_t) = (71/32.2)*a*1.8 (eq2)

a = (32.2*cos68)/1.8 = 6.701 rad/s^2

Sum moments about the center of gravity: Ta*(cos22)*2.05 - Tb*(cos22)*0.65 = 0 (eq3)

2.05Ta = 0.65Tb

Solve (eq1) and (eq3) for Ta and Tb:

Ta = 15.85 lb

Tb = 49.98 lb

a = 6.701 rad/s^2