A boy ties a 500kg rock to a 1.0m long string and swings it around his head in a horizontal circle. At what angular velocity, in rpm, does the string tilt down at a 10 degree angle?(adsbygoogle = window.adsbygoogle || []).push({});

sintheta = mg / T

sin10 = 0.5kg(9.8m/s^2) / T

T = 4.9N / sin10

T = 28.22N

THEN...

v = SqRt [(rTcostheta) / m] ---> However the radius of the circle is not the length (L) so, r = Lcostheta

v = SqRt [(LTcos^2 theta) / m]

v = SqRt [(1.0m)(28.22N)(cos10^2) / 0.5kg]

v = 7.4m/s

FINALLY...

OMEGA = v / r

= v / Lcostheta

7.4rad / 1sec x 1rev / (2pi)rad x 60sec / 1 min --> rad and sec cancel out, leaving...

= 70.7 rpm

This was my initial attempt to the problem but I am not sure if everything is correct?

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# Homework Help: Motion In A Circle

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