The grinding disc of a grinding machine starts from a rest and has a constant angular acceleration for the first 10 rotations.

a) It uses 0.87 s on its second rotation. how long does it use on the first rotation?

Her i found out that it use 0.62s on the first rotation!

b) What is the angular acceleration of the disc for the 10 rotations. give the answer in radians / s ^ 2?

is this the right formula to use?

∝=(ω_1-ω_0)/(t_1-t_0 )

Do i need to find out the time it use on the 10 rotasion?