MHT CET 2020 Physics Solved Paper

δ=‌

Wℓ3

3YI

, where W= load, ℓ= length of beam and I is geometrical moment of inertia for rectangular beam,
I=‌

bd3

12

where b= breadth and d= depth
For square beam b=d
∴‌‌I1=‌

b4

12

For a beam ofcircular cross-section, I2=(‌

πr4

4

)
∴‌‌δ1=‌

Wℓ3×12

3Yb4

=‌

4Wℓ3

Yb4

(for sq. cross-section)
and δ2=‌

Wℓ3

3Y(πr4∕4)

=‌

4Wℓ3

3Y(πr4)

(for circular cross-section)
Now ‌

δ1

δ2

=‌

3πr4

b4

=‌

3πr4

(πr2)2

=‌

3

π

(∵b2=πr2 i.e., they have same cross-sectional area)