Centre of Gravity problem

[Khaldoun-Habboub]

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

[Fu-Kwun Hwang]

May be I did not fully understand your question.
But why the weight of the rule will be changed when suspended from different points?

[Khaldoun-Habboub]

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. :!:

[hy2220N11411E]

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.

[bluebearqq]