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A motorist is driving at 20m/s when she sees that a traffic light 200m ahead has just turned red. She knows that this light stays red for 15s, and she wants to reach the light just as it turns green again. It takes her 1.0s to step on the brakes and begin slowing.
What is her speed as she reaches the light at the instant it turns green?

Respuesta :

adelekeademolu

Answer:

8.57 m/s

Explanation:

let's list out available parameters:

Initial velocity, u = 20 m/s

Time = 15 - 1 = 14 s

Distance, s = 200 m

Final velocity = ?

We are assuming a uniformly accelerated motion.

Using one of the equations of motion [tex]s = \left(\dfrac{u+v}{2}\right)t[/tex]

[tex]v = \dfrac{2s}{t}-u[/tex]

[tex]v=\dfrac{2\times200}{14}-20[/tex]

[tex]v=28.6 - 20[/tex]

[tex]v=8.6[/tex] m/s

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