torque questions

[darkangelthn]

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Was wondering if someone can help me with torque. I under stand the torque equation, but somehow i can't solve the problem. In the EK physics practive prob 60: There is a 1m board, hands in static eq. from a rope with tension T. A block hangs by a string on the left of the board w/mass of 3kg. Distance from block to T is .2m. What is the mass of the board?

The explanation: using the left side with block as point of rotation. 3kg*.2m = T*.3m --> T=2kg

i don't understand where the .3m comes from? can someone explains this problem to me a little more than what the explanation did

 

[darkangelthn]

nevermind on the question above. I know what the .3m is now.

 

[FrkyBgStok]

It is good that you got it, but the EK torque strategy sucks.

 

[Mcat35]

It is good that you got it, but the EK torque strategy sucks.

ya on something like this where board comes into play the left end as pivot would probably be the best though since the T is not at the center of the mass of the board.

If it was at the center of mass than i find it easier to just use the T as pivot.

but main thing is to know that Torque CCW has to equal Torque CW for it to be in static equilibrium.