Question

A uniform metre rule AB has a knife edge balanced at 60m away from B,when a lead of 22g is kept 10m away from A,what is the weight of the metre rule?

Answer 1

66 g

Explanation:

The drawing that represents the situation is as follows:

The first thing is to calculate the force at 10 meters (lead), just like this:

`L=10m\cdot22\text{ g}\cdot\frac{1\text{ kg}}{1000\text{ g}}=0.22\text{ N}`

Therefore, from moment of force:

`\begin{gathered} L\cdot30=W\cdot10 \\ W=(30\cdot L)/(10) \\ W=3\cdot0.22=0.66\text{ N} \\ \text{now,} \\ W=\frac{0.66\text{ N}}{10\text{ m}}=0.066\text{ kg = 66 g} \\ \end{gathered}`