A battet dancer spins with 2.8 rps with her arms out stretched. When the moment of inertia about the same axis becomes 0.7 l. the new rate of spin is

Options

A. 3.2 rps
B. 4.0 rps
C. 4.8 rps
D. 5.6 rps

Answer

B

Explanation

Here, `n_(1)="2.8 rps, "n_(2)=? and l_(2)=0.7l_(1)`
`"As "(omega_(2))/(omega_(1))=(l_(1))/(l_(2))=(1)/(0.7)`
`therefore" "(n_(2))/(n_(1))=(10)/(7)`
`n_(2)=(10)/(7)n_(1)=(10)/(7)xx2.8="4.0 rev s"^(-1)`