A car is traveling 20.0 m/s when the driver sees a child standing on the road. She takes 0.80 s to react, then steps on the brakes and slows at 7.0 m/s2. How far does the car go before it stops?

Question

anonymous · Answer

There's two equations you have to keep in mind here for a kinematics problem:
$$v _{f} =v _{0} + at$$$$x _{f} = x _{0} +v _{0}t + \frac{ 1 }{ 2 }at ^{2}$$
The first equation will allow you to determine how much time the car will take before it reaches a velocity of "0 m/s" 

The second equation determines how far the car will go with the time it took to reach that "0 m/s" 

Keep in mind it also took the driver 0.80 seconds for her to respond so this is without the constant deceleration of "7.0 m/s".

In which, we use this equation:$$x = vt$$

So keep in mind that there's TWO parts to this equation.