A car of mass M = 1100 kg traveling at 55.0 km/hourenters a banked turn covered
ID: 1360837 • Letter: A
Question
A car of mass M = 1100 kg traveling at 55.0 km/hourenters a banked turn covered with ice. The road is banked at an angle , and there is no friction between the road and the car's tires as shown in (Figure 1) . Use g = 9.80 m/s2 throughout this problem. What is the radius r of the turn if = 20.0 (assuming the car continues in uniform circular motion around the turn)? Now, suppose that the curve is level (=0) and that the ice has melted, so that there is a coefficient of static friction between the road and the car's tires as shown in (Figure 2) . What ismin, the minimum value of the coefficient of static friction between the tires and the road required to prevent the car from slipping? Assume that the car's speed is still 55.0 km/hour and that the radius of the curve is 65.4 m .
Explanation / Answer
v = 55 x 1000m / 3600sec =15.28 m/s
Ncos20 = mg ( in vertical )
Nsin20 = mv^2 / R ( in horizontal)
tan20 = v^2 /Rg
tan20 = 15.28^2 / R*9.80
R = 65.39 m
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now N = mg
and friction = uN = umg
and in horizontal, f = mv^2 / R
umg = mv^2 / R
u = v^2 / Rg = 15.28^2 / ( 65.4x9.80) =0.36
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