A train is traveling at a speed of 80 km/h when the conductor applies the brakes. The train slows with a constant acceleration of magnitude .5 m/s^2. We want to find the distance the train travels from the time the brakes are applied until the train comes to a complete stop. Which kinematic formula would be most useful to solve for the target unknown?

Respuesta :

Answer:

The train will travel 493.817 meters until it stops completely.

Step-by-step explanation:

In this case, we know that train applies the brakes and decelerates at constant rate until rest is reached after travelling an unknown distance. Travelled distance ([tex]\Delta s[/tex]), measured in meters, can be found by using this kinematic formula:

[tex]v^{2} = v_{o}^{2}+2\cdot a \cdot \Delta s[/tex] (Eq. 1)

Where:

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

[tex]v[/tex] - Final speed, measured in meters per second.

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

Now travelled distance is cleared within the formula:

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

If we know that [tex]v_{o} = 22.222\,\frac{m}{s}[/tex], [tex]v = 0\,\frac{m}{s}[/tex] and [tex]a = -0.5\,\frac{m}{s^{2}}[/tex], then the distance travelled by the train is:

[tex]\Delta s = \frac{\left(0\,\frac{m}{s} \right)^{2}-\left(22.222\,\frac{m}{s} \right)^{2}}{2\cdot \left(-0.5\,\frac{m}{s^{2}}\right) }[/tex]

[tex]\Delta s = 493.817\,m[/tex]

The train will travel 493.817 meters until it stops completely.

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