# 1) The ratio of the angular speeds of the hour hand and the minute hand of a clock is{answer should come 1:12}2) Two particles A and B move in concentric circles of radii respectively in such a way that A, B and the centre of the circle (O) always lie on a straight line. The ratio of their angular velocities is{answer should come one}3) The angular speed of a flywheel rotating at 90 r.p.m. is{answer should come 3 rad/s}4) A flywheel of diameter 1 m is rotation at 600 r.p.m. The acceleration of a point on the rim of the fly wheel is{answer should come 200 }

1
by alwaz

2014-09-27T15:47:41+05:30

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The hours hand rotates full circle in 12 hours. So it covers an angle 360⁰ in 12 hours. Minutes hand covers a full circle in 12 hrs.

angular velocity of hours hand =  2π/(12*3600) radians/sec
angular velocity of minutes hand = 2π/3600  radians / sec
so ratio =  1 : 12

2)  see diagram.
The two particles are in a straight line always.  It means they cover the same angle θ in same time duration.  so angular velocities are ω1 = θ/time = ω2
so ω1 = ω2

3) angular speed or velocity =  angle / time = 90 * 2 π / 60 = 3π rad/sec

4) angular velocity of the point = angle / time = 600 * 2π / 60 = 20 π rad/sec
centripetal acceleration towards the center of circle