# NEET Physics Mathematical Tools Questions Solved

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

1. $\frac{{\mathrm{\pi a}}^{2}}{2}$

2. ${\mathrm{\pi a}}^{2}$

3. $\frac{3}{2{\mathrm{\pi a}}^{2}}$

4. $2{\mathrm{\pi a}}^{2}$

Concept Videos :-

#16 | Calculus: Differential Equation
#19 | Numericals

Concept Questions :-

Integration

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 $2\mathrm{\pi r}$ and thickness dr.

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

=

Difficulty Level:

• 16%
• 66%
• 4%
• 16%
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