COMEDK Exam 2022 Solved Paper

As per formula, the Young's modulus, γ=

stress

strain

=

F A

Δl l

⇒ F=

γAΔl

l

In first case, γ=

F A1

l1 L

⇒ F=

γl1A1

L

............(i)
Similarly, for the second case,
F=

γl2A2

Δl

...............(ii)
From Eqs. (i) and (ii), we get

γl1A1

L

=

γl2A2

4L

As γ is same, as the same material is taken, l1A1=

l2A2

4

l1πr2=

l2

4

π(4r)2
l1=

l2

4

.

16r2

r2

=4l2⇒l2=

l1

4

Hence, l1=l,l2=

l1

4