Angular motion homework problem

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SUMMARY

The discussion revolves around solving an angular motion problem involving an electric motor and a grinding wheel. The motor operates at 90 revolutions per minute (rev/min) and experiences a constant negative angular acceleration of 2.50 rad/s². The correct time to stop the wheel is calculated as 3.77 seconds. The user initially miscalculated the angular displacement (theta) due to an extra negative sign, leading to an incorrect answer of -17.766 radians.

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  • Understanding of angular motion equations
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  • Knowledge of converting revolutions per minute to radians per second
  • Proficiency in algebraic manipulation of equations
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  • Study the kinematic equations for rotational motion
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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.
 
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uuh lol never mind i just had an extra negative sign
 

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