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

Question

A red train traveling at 72 km/h and a green train traveling at 144km/h are headed toward each other along a straight, level track.When they are 820 m apart, each engineer sees the other's train andapplies the brakes. The brakes slow each train at the rate of 1.0m/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 theycollide (0 m).
If not, give (a) the speed of the red train (0m/s), (b) the speed of the green train (0 m/s),and (c) the separation between the trains whenthey stop.

Explanation / Answer

A red train traveling at 72 km/h and a green train traveling at 144km/h are headed toward each other along a straight, level track.When they are 820 m apart, each engineer sees the other's train andapplies the brakes. The brakes slow each train at the rate of 1.0m/s2. Is there a collision? relative speed =72+144=216km/h=216*5/18=60m/sec distance=820m a=-2m/sec2final velocity=0m/sec 0-3600/-4=900m hence the distance present is not sufficient . so there will be collision. If so, give (a) the speed of thered train, (b) the speed of the green train, and(c) the separation between the trains when theycollide (0 m). time elapsed to cover 820m before collision=820=60*t+1/2*2*t*t calculating t=11.47sec in this time speed of redtrain=u-at=72*5/18-1*11.47=20-11.47=8.53m/sec speed of green train=144*5/18-1*71.47=40-11.47=28.53m/sec separation=0m

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