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Friction provides the force needed for a car to travel around a flat, circular race track. What is the maximum speed at which a car can safely travel if the radius of the track is 84.0 m and the coefficient of friction is 0.42?

Respuesta :

Answer:

The maximum speed at which the car can safety travel around the track is 18.6m/s.

Explanation:

Since the car is in circular motion, there has to be a centripetal force [tex]F_c[/tex]. In this case, the only force that applies for that is the static frictional force [tex]f_s[/tex]between the tires and the track. Then, we can write that:

[tex]f_s=F_c[/tex]

And since [tex]f_s\leq \mu N[/tex] and [tex]F_c=\frac{mv^{2}}{r}[/tex], we have:

[tex]\mu N\geq \frac{mv^{2}}{r}[/tex]

Now, if we write the vertical equation of motion of the car (in which there are only the weight and the normal force), we obtain:

[tex]N-mg=0\\\\\\implies N=mg[/tex]

Substituting this expression for [tex]N[/tex] and solving for [tex]v[/tex], we get:

[tex]\mu mg\geq \frac{mv^{2}}{r}\\\\v\leq \sqrt{\mu gr}[/tex]

Finally, plugging in the given values for the coefficient of friction and the radius of the track, we have:

[tex]v\leq \sqrt{(0.42)(9.81m/s^{2})(84.0m)}\\\\v\leq 18.6m/s[/tex]

It means that in its maximum value, the speed of the car is equal to 18.6m/s.

Answer:

[tex]v=18.6 m/s[/tex]

Explanation:

We need to equal the friction force and the centripetal force:

[tex]F_{f}=F_{c}[/tex]

[tex]\mu N=ma_{c}[/tex]

  • N is the normal force (N = mg)
  • μ is the coefficient of friction (0.42)
  • a(c) is the centripetal force (a_{c}=v^{2}/R)

[tex]\mu mg=m*\frac{v^{2}}{R}[/tex]

[tex]\mu g=\frac{v^{2}}{R}[/tex]

[tex]v=\sqrt{R\mu g}[/tex]

[tex]v=\sqrt{84*0.42*9.81}[/tex]

[tex]v=18.6 m/s[/tex]

I hope it helps you!