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JDK1.0.2 simulations (1996-2001) => Dynamics => Topic started by: Khaldoun-Habboub on February 20, 2006, 06:02:14 pm



Title: Centre of Gravity problem
Post by: Khaldoun-Habboub on February 20, 2006, 06:02:14 pm
Hey,
If a uniform metre rule has a 4N weight hanging from one end, and the rule balances when suspended from a point 0.1m from that end. What would be the weight of the rule??? cheers


Title: topic338
Post by: Fu-Kwun Hwang on February 21, 2006, 10:27:28 am
May be I did not fully understand your question.
But why the weight of the rule will be changed when suspended from different points?


Title: Strange ha!!
Post by: Khaldoun-Habboub on February 22, 2006, 04:17:45 pm
You are absolutely right, but the question was stated exactly the same way I stated above.
It came from a physics text book by Oxford. :!:


Title: topic338
Post by: hy2220N11411E on March 23, 2006, 12:45:26 am
The orginal question should be interpreted this way:
a uniform metre rule (or ruler) means a beam of 1 metre in length;
a 4N weight (a separated heavy object) being hanged from one end, exerting a downward force;
the rule is being hanged 0.1m from the end with the 4N weight, exerting an upward force (the tension);
uniform metre rule means the CG (centre of gravity) is 0.5m from either end, and the weight of the rule is producing another downward force;

Let W = weight of the rule, T = the tension to "hang" the rule

taking moment about the end with the "4N weight", then
(0.1)(T) = (0.5)(W)

all upward forces = all downward forces, then
T = W + 4

by solving the simultaneous equations
W = 1

so the weight of the rule is 1 N
 


Hope my words help.
Cheers.


Title: Re: Centre of Gravity problem
Post by: bluebearqq on February 20, 2011, 05:56:51 am
 :)