Question

a car is moving at a constant velocity of 20 m/s when the driver hits the brakes because she sees and an animal run across the street in front of her. the car experiences an acceleration of - 2.5 m/s² and the driver brakes for 2 seconds before taking her foot off the brake pedal. how fast will the car be moving? (a) 15 m/s (b) 17.5 m/s (c) 12.5 m/s (d) 7.5 m/s

Explanation:

Step1: Identify the kinematic - equation

We use the equation \(v = v_0+at\), where \(v_0\) is the initial velocity, \(a\) is the acceleration and \(t\) is the time.

Step2: Substitute the given values

Given \(v_0 = 20\ m/s\), \(a=- 2.5\ m/s^2\) and \(t = 2\ s\).
\[v=20+( - 2.5)\times2\]
\[v = 20 - 5\]
\[v=15\ m/s\]

Answer:

15 m/s