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MasteringPhysics: Ch 4-Hw# 1 . Google Chrome tt s/isession.masteringphysics.com/myct/itemview2assignmentProblemID-60994304 https:// ements of Physics-Herat (Spring 2016) 4 HE Problem 462 roblem 4.62 Part A A car has a mass of 1500 kg if the driver applies the brakes White on a gravel road, he maxim ricion force that the tires can provide without skidding is about 7000 N lfhe car is moving at 30 m/s what ste shortestdistance in which the car can stop safely? Express your answer to two significant figures and include the appropriate units. Value Units ON

Explanation / Answer

The horizontal forces acting on the car are: the braking (friction) force opposing car's movement and the inertial force which tends to keep the car moving. The two forces have equal intensity and opposite directions. That means that the friction force equals the inertial force:
Ff = Fin
Ff = m*a
Solving for acceleration:
a = Ff/m = 7000/1500 = 4.67 m/s^2
Velocity (car speed), uniform acceleration and space are linked by the following formula:
v^2 = 2as
Solving for s:
s = V^2/(2a) = 30^2/(2*4.67) = 96.36 m
which is the shortest safe stopping distance for the car.

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