On 10/19/2005 10:25:48 PM, mdao wrote:
>Hey, I was hoping somebody
>could give me some help on
>this question. I tried it
>many times but could not get
>it. Most likely my units are
>off or possibly using the
>wrong formula/ equation.
>Here it is:
>
>The tires of a car make 65
>revolutions as the car reduces
>its speed uniformly from 95
>km/h to 45 km/h. The tires
>have a diameter of 0.80m. (a)
>What was the angular
>acceleration of the tires?
>(b) If the car continues to
>deccelerate at this rate, how
>much more time is required for
>it to stop?
>
>Okay, I changed the unif.
>speed into m/s, I wasn't too
>sure if I should, but I I
>changed 65 rev into 9420 rads.
>Anyway I thought of using this
>formula
>w^2= w(initial)^2 + 2*(angular
>accel.)*(angle)
>I'm not too sure if it is the
>correct formula since it does
>not require the use of the
>diameter or radius. Okay,
>thanks for the help.
Why that one? This should be the same as if the velocities were linear velocities
distance traveled = w_{i}+acc*t^{2}/2
and w_{f} = w_{i} + acc*t
substituting for acc*t in the first equation allows you to find the time duration of the deceleration. In order to figure out the angular velocity, you need to use the radius.
TTFN,
Eden