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Estimating Car's Initial Speed from Skid Marks: A Physics Explanation
Chapter 4, Problem 70(choose chapter or problem)
Police investigators, examining the scene of an accident involving two cars, measure 72-m-long skid marks of one of the cars, which nearly came to a stop before colliding. The coefficient of kinetic friction between rubber and the pavement is about 0.80. Estimate the initial speed of that car assuming a level road.
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QUESTION:
Police investigators, examining the scene of an accident involving two cars, measure 72-m-long skid marks of one of the cars, which nearly came to a stop before colliding. The coefficient of kinetic friction between rubber and the pavement is about 0.80. Estimate the initial speed of that car assuming a level road.
ANSWER:Step 1 of 3
Consider the given data as follows:
The long skid marks of one of the car is measured by s=72 m.
The coefficient of kinetic friction between rubber and pavement is about \(\mu =0.80\).
According to Newton’s Second law
\(F=m\cdot a\)
For gravitation, the force will be defined using Newton's second law. the force will be
\( F=-\mu N \)
\( F=-\mu mg\)
Where the coefficient of friction is \(\mu\), the mass of the car is \(m\), and \(g\) is the acceleration due to gravity \(\left( =9.8\ \dfrac{\text{m}}{{{\text{s}}^{\text{2}}}} \right)\), and \(a\) is the acceleration of the car.
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Estimating Car's Initial Speed from Skid Marks: A Physics Explanation
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Estimate a car's initial speed from skid marks using physics principles. Apply Newton's Second Law and equations of motion to deduce the initial velocity. Understand the role of frictional force in car deceleration during accidents.