Calculating Car Speed After Sudden Braking

[012435]

Homework Statement

driver slams breaks. car slows with acceleration of -5.6m/s^2 for 4.20s for 62.4m.

Homework Equations

with wat speed does the car then strike an object?

The Attempt at a Solution

i thought of using equation Xf=Xi+Vi(t)+1/2at^2
i am not sure if this is the best choice but when using this i am getting stuck with the initial velocity. am i in the right track

 

[learningphysics]

Yes, you can use that equation. Find vi, then you can find vf...

 

[m2003]

?

I would suggest using the equation v^2 = u^2 + 2as, where v is the final velocity, u is the initial velocity, a is the acceleration, and s is the distance traveled. In this case, we know the acceleration (-5.6m/s^2), the distance traveled (62.4m), and the time (4.20s). We can rearrange the equation to solve for the final velocity (v), which will give us the speed of the car after the sudden braking. This equation assumes that the initial velocity is 0, which is a reasonable assumption if the car was traveling at a constant speed before the sudden braking. Therefore, the final velocity would be √(2*(-5.6m/s^2)*(62.4m)) = -16.8m/s. This indicates that the car would be traveling at a speed of 16.8m/s (or approximately 60.5km/h) when it strikes an object after the sudden braking.