How Long Does It Take for a Flywheel to Reach 125 Rev/Min from Rest?

[MMCS]

A flywheel 1.2 m in diameter is uniformly accelerated from rest and revolves completely 68 times in reaching a speed of 125 rev/min. Find the time taken to reach this speed

i have been given the correct answer as 65.29 seconds

Wht i have up to now

ω1 = 0
ω2 = 125 r/min = 125/60 = 2.083 r/s
theta = 68*2∏ = 427.26 rads
t = ?

I have tried to use theta = ((ω1+ω2)*t)/2 rearranged to get t = 2theta/ω1+ω2 however my answer doesn't come close

Any suggestions would be appreciated

 

[TxRationalist]

you need the equation of motion for rotation. the flywheel is undergoing uniform acceleration; you need to take that into consideration.

 

[Doc Al]

ω1 = 0
ω2 = 125 r/min = 125/60 = 2.083 r/s

Make sure ω is in rads/sec.

 

[MMCS]

That sorted it, silly mistake, Thanks Doc Al