A red train traveling at 72 km/h and a green train traveling at 144 km/h are hea

Question

A red train traveling at 72 km/h and a green train traveling at 144 km/h are headed toward each other along a straight, level track. When they are 870 m apart, each engineer sees the other's train and applies the brakes. The brakes slow each train at the rate of 1.0 m/s2. Is there a collision? If so, give (a) the speed of the red train, (b) the speed of the green train, and (c) the separation between the trains when they collide (0 m). If not, give (a) the speed of the red train (0 m/s), (b) the speed of the green train (0 m/s), and (c) the separation between the trains when they stop (a) Number Units Units (c) Number( DUnitsG Click if you would like to Show Work for this question: Open Show Work

Explanation / Answer

relative speed = 72 + 144 = 216 kmph

= 60 m/s

d = 870 m

a = 1 m/s2

the final velocity = 0

0 - 3600 / - 4 = 900 m

so there is chance for the collision

then

870 = 60 t + 0.5 t2

t = 16.87 sec

speed of red train = u - a t

= 20 - 1 X 16.87

= 3.13 m/s

speed of green train = 40 - 16.87

= 23.23 m/s

the separation is ZERO

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