A 1500 kg car decelerates from an initial velocity of 19 m/s to a skidding stop. If the coefficient of kinetic friction is 0.100, how long are the skid marks?

Respuesta :

Answer:

19.4 seconds

Explanation:

We have:

m: mass of the car = 1500 kg

v₀: is the initial speed = 19 m/s    

[tex]v_{f}[/tex]: is the final speed = 0 (it stops)

[tex]\mu_{k}[/tex]: is the coefficient of kinetic friction = 0.100

First, we need to find the acceleration by using the second Newton's law:

[tex] \Epsilon F = ma [/tex]              

[tex] -\mu_{k}N = ma [/tex]

[tex] -\mu_{k}mg = ma [/tex]

Solving for a:

[tex] a = -\mu_{k}g = -0.1*9.81 m/s^{2} = -0.981 m/s^{2} [/tex]

Now we can find the time until it stops:

[tex] v_{f} = v_{0} + at [/tex]

Solving for t:

[tex] t = \frac{v_{f} - v_{0}}{a} = \frac{-(19 m/s)}{-0.981 m/s^{2})} = 19.4 s [/tex]

 

Therefore, the time until it stops is 19.4 seconds.

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