As we know in the absence of external torque, angular momentum is constant so, L‌initial ‌=L‌final ‌ m1(r1×v1)=m2(r2×v2) since, ‌‌v=rω ⇒‌‌m1ω1r12=m2ω2r22 For earth mass remain constant (i.e., m1=m2 ) ⇒‌‌ω1r12=ω2r22‌‌(∵ω=‌