Question

A red train traveling at 72 km/hr and a green train traveling at 144 km/hr are headed toward one another along a straight level track. When they are 950 meters apart, each enginneer sees the other's train and applies the brakes. The brakes decelerate each train at the rate of 1.0 m/s^2. Is there a colllision? If so, what is the speed of each train at impact? If not, what is the separtion between the trains when they stop??

Answer 1

For red train:
v^2-u^2=-2as
0-400=-2s
s=200m
Red train travels 200m..

For green train:
v^2-u^2=-2as
0-1600=-2s
s=800m
Red train travels 800m..

Hence..they will collide because..800+200=1000m>950m(initial seperation)

Answer 2

clear?

Answer 3

but what was the speed of the trains when they collided?

Answer 4

Red=>72km/hr=20m/s
Green=>144km/hr=40m/s

Answer 5

No i meant, when the two trains collided..

Answer 6

0

Answer 7

You can do this via Relative Velocity too

Answer 8

That is a one line answer :)

Answer 9

if the speed was 0, they would have stopped tho..

Answer 10

We are only asked if they collide..so we assume final velocity=0

Answer 11

haha it said "Is there a colllision? If so, what is the speed of each train at impact?"

Answer 12

so 0 :)

Answer 13

not sure..

Answer 14

wait

Answer 15

but 0 means they trains are stopped. so there won't be a collision and the answer would be "no".

Answer 16

there you go o.O

Answer 17

hmm.. what is 35.83m/s?

Answer 18

final velocity of red train!

Answer 19

so it actually becomes faster??

Answer 20

even tho it's braking?

Answer 21

u have the answer key?

Answer 22

a=-1 not 1!

Answer 23

v=u-at

Answer 24

you have 3 things

Answer 25

I know that they collide and red train stops

Answer 26

I just need to know the speed of the green train at the point of the impact.

Answer 27

Consider red train to be at rest and apply relative velocity
u have 3things

Answer 28

??

Answer 29

what's the ans

Answer 30

i don't know.......