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The coefficient of kinetic friction between the tires of a car and a horizontal road surface is 0.52. If the car is traveling at an initial speed of 25 m/s, and then slams on the breaks so the car skids straight ahead to a stop, how far does the car skid?

Sagot :

Answer:

The car skids in a distance of 61.275 meters.

Explanation:

Since the only force exerted on the car is the kinetic friction between the car and the horizontal road, deceleration of the vehicle ([tex]a[/tex]), measured in meters per square second, is determined by the following expression:

[tex]a = \mu_{k}\cdot g[/tex] (1)

Where:

[tex]\mu_{k}[/tex] - Coefficient of kinetic friction, no unit.

[tex]g[/tex] - Gravitational acceleration, measured in meters per square second.

If we know that [tex]\mu_{k} = 0.52[/tex] and [tex]g = -9.807\,\frac{m}{s^{2}}[/tex], then the net deceleration of the vehicle is:

[tex]a = 0.52\cdot \left(-9.807\,\frac{m}{s^{2}} \right)[/tex]

[tex]a = -5.1\,\frac{m}{s^{2}}[/tex]

The distance covered by the car is finally calculated by this kinematic expression:

[tex]\Delta s = \frac{v^{2}-v_{o}^{2}}{2\cdot a}[/tex] (2)

Where:

[tex]v_{o}[/tex], [tex]v[/tex] - Initial and final speed, measured in meters per second.

[tex]a[/tex] - Net deceleration, measured in meters per square second.

If we know that [tex]v_{o} = 25\,\frac{m}{s}[/tex], [tex]v = 0\,\frac{m}{s}[/tex] and [tex]a = -5.1\,\frac{m}{s^{2}}[/tex], then the distance covered by the car is:

[tex]\Delta s = \frac{\left(0\,\frac{m}{s} \right)^{2}-\left(25\,\frac{m}{s} \right)^{2}}{2\cdot \left(-5.1\,\frac{m}{s^{2}} \right)}[/tex]

[tex]\Delta s = 61.275\,m[/tex]

The car skids in a distance of 61.275 meters.