# JEE mechanics doubt!! plz help

Q. If angular velocity of a disc depends on angle rotated $$\theta$$ as $$\omega$$ =$$\theta^{2}$$ +$$2\theta$$, then its angular acceleration $$\alpha$$ at $$\theta$$=1 rad is

(1) 8 rad/$$sec^{2}$$
(2) 10 rad/$$sec^{2}$$
(3) 12 rad/$$sec^{2}$$
(4) None of these

Note by Akhilesh Chobey
4 years, 1 month ago

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since a(alpha) = dw/dt = (dw/ds )(ds/dt)=w(dw/ds).Hence ans will be 3*4=12

- 2 years, 9 months ago

i think angular acc is dw/dt to find that : first find dw/dtheta and then as we know w = dtheta/dt

so now take out inverse of w which is dt/dtheta and now divide dw/dtheta and dt/dtheta

- 2 years, 11 months ago

First differentiate omega with respect to t to get the expression of alpha then put the value of omega at theta 1 and theta

- 3 years, 9 months ago