Solving Kinematics Problems: Distance Traveled Before Applying Brakes

[nblu]

Q: The average alcohol-free driver requires about 0.8 s to apply the brakes
after seeing an emergency. Calculate the distance traveled after seeing the emergency
before applying the brakes.

with the question, the given speed is 17 m/s and t = 0.8.
at first, i used d =vt equation to find the distance, however,
when i read through the question again, i had a feeling that it's not right.
my first answer was d=14m, but it just doesn't look correct.

i was thinking of finding the acceleration then use v^{2}_{f}=v^{2}_{i} +2a\Deltad
to solve for d, OR, use this equation, \Deltad=1/2(v_{1}+v_{2})\Deltat, without
even having to find the acceleration.

one part of my knowledge tells me that i don't need acceleration to do this question
because this is about "before" applying the break.

its confusing me..

any help would be greatly appreciated.

thank you

 

[Dick]

You "know" what you did is right. Resist the temptation to complicate it. I'm sure you'll get a chance to use that other stuff later.

 

[Siracuse]

with the question, the given speed is 17 m/s and t = 0.8.
at first, i used d =vt equation to find the distance, however,
when i read through the question again, i had a feeling that it's not right.
my first answer was d=14m, but it just doesn't look correct.

one part of my knowledge tells me that i don't need acceleration to do this question
because this is about "before" applying the break.

If Dick's reply isn't enough, your logic is right to me, simple enough. I don't see how it doesn't "look correct".

 

[nblu]

You "know" what you did is right. Resist the temptation to complicate it. I'm sure you'll get a chance to use that other stuff later.

If Dick's reply isn't enough, your logic is right to me, simple enough. I don't see how it doesn't "look correct".

Thank you, I really appreciate it! :)