A coin is placed 12.0 cm from the axis of a rotating turntable of variable speed. When the speed of the turntable is slowly increased, the coin remains fixed on the turntable until a rate of 39.0 rpm (revolutions per minute) is reached, at which point the coin slides off.

fs = m / R

   = mR    ........... where w = 2f

then fs = µsN = µs×mg = R

µs = R/g , since w = 2f = 2× 39.0

                                            = 4.084

µs = 0.12× / 9.8

     =  0.204

Explanation:

when using this equation it is important to look at the units you working with so that it would be much easier to workout the solution.

a high pressure system is a dense air mass that is usually cooler and drier than the surrounding air. a low pressure system is a less dense air mass that is usually wetter and warmer than the surrounding air.

in general, areas that experience high atmospheric pressure also experience fair weather. low pressure systems can cause the formation of clouds and storms. air usually flows from areas of high pressure to areas of low pressure..