NEET Physics Mathematical Tools Questions Solved


Calculate the area of disk of radius 'a' using integration

1. πa22

2. πa2

3. 32πa2

4. 2πa2

Concept Videos :-

#16 | Calculus: Differential Equation
#19 | Numericals

Concept Questions :-

A disk of radius a can be assumed to be made of infinite concentric rings each of small thickness dr. Now consider a ring of inner radius r and outer radius r+dr. If we cut out this smalll ring, cut it along the radius and straighten it out, we obtain a rectangle of length 2πr and thickness dr.

 dA=2πrdr

Total area of disk A= 0r2πrdr [Since radius of innermost ring is zero and that of outer most is a]

==2πr220a =2πa22=πa2

Difficulty Level:

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