The coefficient of static friction between a rubber tire and dry pavement is abo

Question

The coefficient of static friction between a rubber tire and dry pavement is about 0.80. Assume that a car's engine applies force equally between the four wheels and the weight of the car is uniformly distributed over all four wheels. (a) What limit does the coefficient of static friction place on the time required for a car to accelerate from rest to 60 mph (26.8 m/s)? s (b) How can friction accelerate a car forward when friction opposes motion? It cannot as friction always opposes the motion of an object. Friction always causes objects to increase in speed. Static friction opposes the relative slipping motion between two surfaces.

Explanation / Answer

a) friction = uN = umg

a = F/m = ug = 0.80*9.8= 7.84 m/s^2

Now

using

v = u + at

t = (26.8-0)/7.84 = 3.42 s

b) It cannot as friction always opposes the motion of an object. Friction always causes objects to decrease in speed. Static friction opposes the relative slipping motion between two surfaces.

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