Finding the angular displacement

[Schu]

Here's the question:
the rotor of a helicopter starts from REST and reaches it's operating speed in 7.28s If the angular acceleration of the rotor is 92.5 rad/s^2, what is the angular displacement during that time?

I'm not sure where to start.
If I multiply the time by the acceleration I would get the velocity only in rad/s.
But then I was thinking more like:
Angular position= 1/2 (angular acceleration) *t^2+(initial angular velocity)*t+(initial angular position)

If I plug them into the angular position formula I get 2451.176 rad

Is the angular displacement a fancy way to say angular position??
Is this the right track to be on?

 

[arildno]

It's definitely the right track!
(displacement=new position minus old position, so by assuming old angular position 0, the angular displacement equals the new angular position)

 

[M98Ranger]

Yes, you are on the right track! Angular displacement is the change in angular position, so you can use the formula you mentioned to calculate the angular displacement. In this case, you would need to use the initial angular velocity of 0 since the rotor starts from rest. Plugging in the values, the angular displacement would be 2451.176 rad, which is also the final angular position after 7.28s. Good job!