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March 3, 2015

March 3, 2015

Posted by **Anonymous** on Saturday, October 11, 2008 at 8:53pm.

- Physics -
**bobpursley**, Saturday, October 11, 2008 at 9:40pmYou have to write equations about arbritary points, but it is very convenient.

I will do one for you, about the right end.

-69.5g*2/6*2.4-22.3g*1.2 + Tl*2.4 =0

You do the left equation.

Dont forget the sum of vertical forces..

Tl+Tr -22.3g-69.5g=0

- Physics -
**drwls (quitting)**, Saturday, October 11, 2008 at 9:50pmLet T1 be the tension in the left rope and T2 be the tension in the right rope. A vertical force balance tells you that

T1 + T2 = (M1+M2)g = (69.5 + 22.3)* (9.8) N

You don't need that equation to solve for T2.

You can use the fact that the torque about the point where the left rope meets the scaffold is zero. The weight of the scaffold acts at the midpoint, which is 1.6 m from the left end. Therefore

M1*g*1.6 m = T2* 2.4 m

Solve for T2 (in Newtons)

- Physics -
**Anonymous**, Saturday, October 11, 2008 at 10:44pmi still have a few questions

1) wouldn't the 1.2 be 1.6 instead?

2) and how come the first equation equals zero. isn't it somewhat of a rearrangement of the second equation, so wouldn't it equal Tr?

- Physics -
**Anonymous**, Saturday, October 11, 2008 at 10:53pmusing drwls method i got 454N and it was wrong

- Physics -
**drwls**, Sunday, October 12, 2008 at 12:23amWhoops. I forgot the torque due to the scaffold's weight, on the left side of the equation, which is 22.3 kg*1.2 m * 9.8 m/s^2. That's why my equation gave you the wrong answer.

- Physics -
**Anonymous**, Sunday, October 12, 2008 at 2:19pmthanx :)

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