# The Equations of Rotational Kinematics

1. Oct 13, 2008

### pstfleur

1. A spinning wheel on a fireworks display is initially rotating in a counterclockwise direction. The wheel has an angular acceleration of -4.00rad/s2. Because of this acceleration, the angular velocity of the wheel changes from its initial value to a final value of -25.0rad/s. While this change occurs, the angular displacement of the wheel is zero. Find the time required for the change in the angular velocity to occur.

2. W=Wo+xt
Displacement=1/2(W+Wo)t
DIsplacement=Wot+1/2xt^2

3. The answer is suppose to be 12.5s..
OK the initial velocity is what I don't have, i know that its going to be negative.. In order for me to get the Initial angular velocity, i need the Time, which I also don't have.. I don't know how to answer with two unknowns.

2. Oct 13, 2008

### pstfleur

hello lol

3. Oct 14, 2008

### pstfleur

bump bump bump

4. Oct 14, 2008

### pstfleur

bumping again for the 2nd day :)