Answer:
Option D
Explanation:
Net external torque on the system is zero. Therefore, angular momentum of the system will remain same.
⇒ l1ω1=(l1+l2)ω2
ω2ω1=l1l1+l2 .....(i)
The energy lost . E1−E2
=12l1ω21−12(l1+l2)ω22
=12ω21[l1−(l1+l2)ω22ω21]
=12ω21[l1−(l1+l2)l21(l1+l2)2]
[ ∵ Eq.(i)]
=12ω21[l21+l1l2−l21(l1+l2)]
=12[l1l2l1+l2]ω21