# Determine the speed of a car when the driver slammed on and locked the brakes.

At an accident scene on a level road, investigators measure a car's skid mark to be 88m long. It was a rainy day and the coefficient of friction was estimated to be 0.42. Use these data to determine the speed of the car when the driver slammed on (and locked) the brakes. (Why does the car's mass not matter?)

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Solution. We can analyze this question as follows. When the driver slammed on the brakes which decreased the speed by the force of friction. We can compute the acceleration, denoted by a. Assume that the mass of the car is M (kg), then the force of friction F can be calculated as ...

#### Solution Summary

The solution includes all the calculations to arrive at an answer to the problem.

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