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A small coin is placed on a stationery horizontal disc at a distance r from its centre. The disc starts rotating about a fixed vertical axis through its centre with a constant angular acceleration alpha. Determine the number of revolutions N, accomplished by the disc before the coin starts slipping on the disc. Find the coefficient of static friction between the coin and the disc is mu_(9). |
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Answer» Solution :we draw the `FBD` of the coin `f_(T)=` tangential component of frictional force on coin `f_(R )=` RADIAL component of frictional force on coin `s` `f_(T)=malphar` `f_(r )=momega_(f)^(2)r` `SQRT(f_(R )^(2)+f_(T)^(2)) LE mu_(g)mg` `2piN=(omega_(f)^(2))/(2alpha)` Solving the equations, we get `N=(((mu_(g)g)/(r )-alpha^(2))^(1//2))/(4pialpha)` |
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