A boy on a cycle pedals around a circle of $20\, metres$ radius at a speed of $20\,metres/\sec .$ The combined mass of the boy and the cycle is $90\, kg$. The angle that the cycle makes with the vertical so that it may not fall is ......... $^o$ $(g = 9.8\,m/{\sec ^2})$
A$60.25$
B$63.90$
C$26.12$
D$30$
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B$63.90$
b (b) $\tan \theta = \frac{{{v^2}}}{{rg}} = \frac{{400}}{{20 \times 9.8}}$
$⇒$ $\theta = 63.9^\circ $
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