Constant Angular Acceleration of a wheel

[hatingphysics]

Starting from rest at t = 0 s, a wheel undergoes a constant angular acceleration. When t = 1.9 s, the angular velocity of the wheel is 6.2 rad/s. The acceleration continues until t = 15 s, when the acceleration abruptly changes to 0 rad/s2. Through what angle does the wheel rotate in the interval t = 0 s to t = 47 s?

okay...there are too many times here..what am i supposed to do for the acceleration after 25sec...to 46secs? i don't know what acceleration to to use to find the angular velocity from 25 to 46secs, to take the total velocity and find the angular displacement.

 

[radou]

Starting from rest at t = 0 s, a wheel undergoes a constant angular acceleration. When t = 1.9 s, the angular velocity of the wheel is 6.2 rad/s. The acceleration continues until t = 15 s, when the acceleration abruptly changes to 0 rad/s2. Through what angle does the wheel rotate in the interval t = 0 s to t = 47 s?

okay...there are too many times here..what am i supposed to do for the acceleration after 25sec...to 46secs? i don't know what acceleration to to use to find the angular velocity from 25 to 46secs, to take the total velocity and find the angular displacement.

Draw a graph, it may help. Since angular acceleration is constant, you know that angular velocity must be a linear function, whose slope you know from the first information given in the problem. The slope is enough to determine the angular acceleration.

 

[Hootenanny]

Split this question up into two phases;

Phase One:Constant Acceleration

From t=0 to t=15, you have a constant angular acceleration, you must calculate this acceleration. You can then use this acceleration to find the angular displacement during this period.

Phase Two:Constant Angular Velocity

From t=15 to t=47 you have a constant angular velocity, which you can calculate from the above phase.

Edit: Radou beat me to it

 

[radou]

Edit: Radou beat me to it

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