Question

find the mass of a thin disc of radius R and density rho equals to kr(thickness -1 )

Answer 1

Hello Dear.

Here is the answer---


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Given ⇒

Radius of the Circular Disc = R
Thickness of the Disc = 1
Density of the Disc = kr

Now, Area of the Circular Disc = $\pi$ × r²
                                                 = (22/7) × (R)²
    
Volume of the Circular Disc = Area × Thickness
                                            = 22 × R²/7


Using the Relation,

    Density = Mass/Volume

⇒ Mass = Density × Volume
⇒ Mass = kr × 22 × R²/7
              = 3.1428 × R²kr



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Hope it helps.

Have a Good Day.

Answer 2

Answer:

Radius of the Circular Disc = R

Thickness of the Disc = 1

Density of the Disc = kr

Now, Area of the Circular Disc =  × r²

                                                 = (22/7) × (R)²

    

Volume of the Circular Disc = Area × Thickness

                                            = 22 × R²/7

Using the Relation,

    Density = Mass/Volume

⇒ Mass = Density × Volume

⇒ Mass = kr × 22 × R²/7

              = 3.1428 × R²kr