Friction and Acceleration problem?

AI Thread Summary
The discussion revolves around calculating the speed of an automobile after the driver locks the wheels while traveling at 15.8 m/s, with a kinetic friction coefficient of 0.760. The friction force is determined using the formula Ffr = μ * FN, where FN is the normal force, which depends on the mass and gravity. A participant notes the challenge of calculating the normal force without mass and suggests using the relationship between friction and acceleration to find the acceleration as a = -μg. The conversation emphasizes applying kinematics to determine the final speed after 1.10 seconds, indicating a need for clarity on the calculations involved. The thread highlights the importance of understanding friction and its effects on motion in physics problems.
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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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