A wheel has a constant angular acceleration of 3.5 rad/s2. During a certain 9.0 s interval, it turns through an angle of 220 rad. Assuming that the wheel started from rest, how long had it been in motion before the start of the 9.0 s interval

It had been 2.48 s before the start of the 9.0 s interval

Explanation: Please see the attachments below

2.5 s

Explanation:

We use the equation of motion for rotational motion:

where

Substituting values,

Before the 9.0 s interval, this value is the final angular velocity. The initial angular velocity is 0 rad/s since it started from rest.

We use the equation:

Note that is the value we got earlier and is the initial angular velocity and is equal to 0 rad/s.

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