Question

Find the angular velocity of a body rotating with an acceleration of 2rev/s^{​​​​​​2} as it completes the 5th revolution after the start.[Concepts of Physics]
BOOK ANSWER - 4.47 rev/s
MY SOLUTION
In one revolution the distance covered is 2π,
so, in 5 revolution the distance moved is 10π
Angular Acceleration = 2rev/s
Initial angular velocity = 0
Final angular velocity = ?
So using equation,
v^{​​​​​​2} = u^{​​​​​​2} + 2as
= 0 + 2* 2*10π
= 40π
v = 11.2rev/sec
Why my Answer is different? Where and what I am missing.
NOTE : I can't write omega on my tablet also you understand it well that we can type only that which is given in keyboard.

Answer 1

From the kinematics of angular motion we can write

ω²=ωo²+ 2αθ
Now substituting
ωo =0
α=2 rev/s²
θ=5 rev

ω²=0 + 2(2 rev/s²)(5)
ω=2√5 rev/s
=2*2.236
=4.472 rev/s