college  physics
posted by ksunhsine on .
was wondering if someone can help me out. Question: a jet has a length of 59.7 meters. The runway on which the plane lands intersects another runway. The width of the intersection is 25m. the plane decelerates through the intersection at a rate of 5.70 m/s^2 and clears it with a final speed of 45 m/s. how much time is needed for the lkplane to clear the intersection?

v_{f}^{2} = v_{i}^{2} + 2ad
(45m/s)^{2} = v_{i}^{2} + 2(5.7m/s^)(25m)
Solve for Vi
Find the average velocity = (v_{i}+v_{f})/2
Divide the width of the intersection by v_{avg} 
Oops, I did not take the length of the plane into account. My first solution shrank the plane to a point concentrated at the end of its tail. I think this can be fixed by changing the distance, d, from 25m to (25+59.7) m.