Torque

Identity · 2008-04-17 01:10:28

In the diagram a plank of length L is balanced on a ridge. What is the maximum value a in terms of L so that the plank will not tip over?

The answer to this is intuitive... a = L/2

But I want to apply torque principles...

The gravitational force is being applied at the centre of mass, which is L/2 of the way along the plank.

So, for the plank to be in equilibrium,

Where

!!!

Help me please, where did I go wrong?

Last edited by Identity (2008-04-17 01:11:33)

Kurre · 2008-04-17 01:27:21

Identity wrote:

[i]

Where did you get the right side from? there is no force mg at that point:/

Identity · 2008-04-17 01:33:39

Hahah... ok i got that bit wrong, but then what am I supposed to put on the RHS?

Dragonshade · 2008-04-17 03:26:59

In my opinion , the only force is mg so Torque = Mgx =0 , therefore x=0 , so the length would be L/2

Identity · 2008-04-17 09:22:37

ok thanks

Dragonshade · 2008-04-17 10:48:02

Wait, I was wrong, Sorry about that

It should be done like this
As the picture

Last edited by Dragonshade (2008-04-17 10:50:04)

Identity · 2008-04-17 18:43:10

Thanks dragonshade, I didn't know you could split forces into fractions of the total length

Dragonshade · 2008-04-18 03:15:43

Identity wrote:

Thanks dragonshade, I didn't know you could split forces into fractions of the total length

hmm, the edge is the fulcrum(pivot), when its unbalance the block will fall off, it would spin around the fulcrum, then I just simple treat it as two object connect with a pipe with the edge as pivot lol

Math Is Fun Forum

#1 2008-04-17 01:10:28

Torque

#2 2008-04-17 01:27:21

Re: Torque

#3 2008-04-17 01:33:39

Re: Torque

#4 2008-04-17 03:26:59

Re: Torque

#5 2008-04-17 09:22:37

Re: Torque

#6 2008-04-17 10:48:02

Re: Torque

#7 2008-04-17 18:43:10

Re: Torque

#8 2008-04-18 03:15:43

Re: Torque

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