A block slides down an inclined surface of inclination 30o with the horizontal Starting (rom rest it covers 8 m in the first two seconds. Find the coefficient of kinetic friction between the two.

Angle of inclination= 30o

Distance travelled (s) = 8m


Time taken (t)= 2 sec


Let us consider the acceleration of the body= a


Initial velocity of the body= 0m/s



Using equation of motion


s=ut + at2




Now, the net force on the body= m.a = m (4)= 4m N


The frictional force experienced by body while moving= f


But, according to the diagram shown, net force on the body is


= mgsin30°-f


= mg-f


Equating the two equations,


= mg-f = 4m


f=0.9 m


Normal force on the body= mgcos30° = (9.8)m= 8.48m


Coefficient of kinetic energy= = 0.11


Hence, coefficient of friction between the surfaces is 0.11


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