Angular motion homework problem

  • Thread starter Dr_bug
  • Start date
  • #1
17
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Homework Statement



An electric motor rotating a workshop grinding wheel at a rate of 90 rev/min is switched off. Assume constant negative angular acceleration of magnitude 2.50 rad/s2.
(a) How long does it take for the grinding wheel to stop?

(b) Through how many radians has the wheel turned during the interval found in (a)?

Homework Equations


wf=wi+at^s
theta= 1/2 (wi+wf)t

The Attempt at a Solution


I got the right answer for (a) which was 3.77 sec so for (b) I thought that all you needed to do was plug in the values into the second equation to get theta but the answer I got was wrong. I got -17.766.....I don't know what I'm doing wrong...any help would be appreciated.
 

Answers and Replies

  • #2
17
0
uuh lol never mind i just had an extra negative sign
 

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