PHYSICS
PHYSICS
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A car is traveling at 72.0 kilometer per hour (km/h) on a flat highway. If the coefficient of kinetic friction between the road and the tires on a rainy day is 0.135, what is the minimum distance needed for the car to stop? Solution Force acting on car f = m a Frictional force f = μ m g Equating the above two m a = μ m g a = μ g a = 0.135 x 9.8 a = 1.32 m/s2 Given velocity 72 km/h = 72 x (5/18) = 20 m/s a is negative, because it retards the motion Using the equation of motion v2– u2 = 2as 202 = 2 (1.32) s 400 = 2.64 s s = 400 / 2.64 s = 151.5 m |