A uniform plank of length 2.00 m and mass 30.0 kg, is supported by three ropes. One rope is attached to the..

Question

...left end and is completely horizontal. The second rope is attached to the left end and is completely vertical. The third rope is attached to the right end and makes an angle of 40.0 degrees with the horizontal. What is the tension in these ropes when a 700N person stands 0.5 meters from the left end?

Answer 1

I drew a picture of the problem for clarity
http://i142.photobucket.com/albums/r88/odu83/plank.jpg

start by summing torque at the right end of the plank

T2*2-700*1.5-30*9.8*1=0
solve for T2
T2=672 N

Now sum torques at the left end
T3*2*sin(40)-700*.5-30*9.8*1=0
solve for T3
T3=501.2 N

Now sum forces in the horizontal
T3*cos(40)-T1=0
solve for T1
T1=384 N

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