Angular motion homework problem

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The discussion revolves around a physics homework problem involving an electric motor's grinding wheel that stops due to constant negative angular acceleration. The user successfully calculated the time it takes for the wheel to stop, which is 3.77 seconds. However, they initially struggled with calculating the angular displacement in radians, resulting in an incorrect negative value. The issue was identified as an extra negative sign in their calculations. The user ultimately resolved the confusion and sought further assistance.
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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
 
Thread 'Correct statement about size of wire to produce larger extension'

Thread 'Correct statement about size of wire to produce larger extension'

The answer is (B) but I don't really understand why. Based on formula of Young Modulus: $$x=\frac{FL}{AE}$$ The second wire made of the same material so it means they have same Young Modulus. Larger extension means larger value of ##x## so to get larger value of ##x## we can increase ##F## and ##L## and decrease ##A## I am not sure whether there is change in ##F## for first and second wire so I will just assume ##F## does not change. It leaves (B) and (C) as possible options so why is (C)...
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