A motorist avoiding hitting a deer

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AI Thread Summary
A motorist traveling at 17 m/s sees a deer 45 m ahead and needs to determine the maximum reaction time to avoid a collision, given a maximum deceleration of -7 m/s². The discussion highlights the use of kinematic equations to calculate the distance traveled during the reaction time and braking phase. A user expresses difficulty in applying the relevant equations and seeks assistance. A hint is provided to focus on calculating the distance covered while braking. The conversation emphasizes the importance of understanding motion equations to solve the problem effectively.
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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
 
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Oh deer!

hsbc2003 said:
A motorist is traveling at 17 m/s …

hi hsbc2003! :smile:

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

Everything else should then become clear. :smile:
 

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