Originally Posted by

**jsu03** Can someone help me with this problem. Thank you very much! Here is what I did so far.

Question: A train is traveling at 100 m/s. The engineer applies the brake b/c he sees a bike on the tracks ahead. The brakes caused a acceleration of -2.2 m/s^2. The enginner applies the brake when the train is 960 m from the bike. How long does it take the train to reach the bike?

Here is what I got so far...

it is asking for time, so I got the equation:

x = x not + v not t + 1/2 a t^2

= 960 + 100t + 1/2 (-2.2)t^2

I use -b +/- squareroot b^2 -4ac / 2a and got a huge number which is incorrect.

Please help me, Im really confused.