A uniform meter stick balances on a fulcrum placed at the 40 cm mark when a weight W is placed at the 30 cm mark. What is the weight of the meter stick?

According to the question,

Let,

We know,

→

Thus the answer above is right.

Learn more about fulcrum here:

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The weight of the meter rule is equal to the weight W placed at the 30cm mark

Explanation:

Detailed explanation and calculation is shown in the image

where is the circuit diagram ?

there is no correct list among the choices you've provided.

the list might look something like this:

-- baby human

-- piccolo

-- flute

-- soprano singer

-- trumpet

-- tenor singer

-- trombone

-- baritone singer

-- baritone horn

-- bass singer

-- tuba

since i had to make up the list myself, i made it easy on myself, and i didn't try to shuffle the string instruments and woodwinds into it too.