Friction and Acceleration problem?

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SUMMARY

The discussion focuses on calculating the speed of an automobile after 1.10 seconds of braking from an initial speed of 15.8 m/s, given a coefficient of kinetic friction of 0.760. The frictional force is derived from the equation Ffr = μ * FN, where FN is the normal force calculated as FN = mass * g. The acceleration due to friction is expressed as a = -μ * g, leading to the conclusion that kinematic equations can be applied to determine the final speed after the specified time interval.

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1. Traveling at a speed of 15.8 m/s, the driver of an automobile suddenly locks the wheels by slamming on the brakes. The coefficient of kinetic friction between the tires and the road is 0.760. What is the speed of the automobile after 1.10 s have elapsed? Ignore the effects of air resistance



2. Ffr=(mu)(FN)
FN=(mass)(g)



3. There is no mass to calculate the normal force. I tried multiplying the acceleration times the friction coefficient and dividing that by the time elapsed but can't get the right answer. ANy help?
 
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Well, friction = \mu m g = -m a \implies a = -\mu g.

Now can you use ordinary kinematics to get the rest of the answer?
 

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