A motorist avoiding hitting a deer

[hsbc2003]

Homework Statement

Part 1:
A motorist is traveling at 17 m/s when he sees a deer in the road 45 m ahead.
If the maximum negative acceleration of vehicle is -7 m/s^2, what is the maximum reaction time (deltat) of the motorist that will allow him to avoid hitting the deer? Answer in units of s.

Part 2:
If his reaction time is 1.71654 s, how fast will he be traveling when he reaches the deer? Answer in units of m/s.

The Attempt at a Solution

I tried to use this equation: X(t)= X (initial)+ V*t + 0.5*a*t^2
but it does not work and I stopped
I can not think of a method to solve it

Please help

Thanks

 

[tiny-tim]

Oh deer!

A motorist is traveling at 17 m/s …

hi hsbc2003!

Hint: Start by working out how far he travels between starting to brake and coming to rest.

Everything else should then become clear.