Physics problem kindly explain how to arrive the answer.

  • #1

Homework Statement


Two trains start at the same time from stations A and B (6km apart ) respectively in opposite tracks. train A accelerates uniformly at the rate of 0.5 meter per second square until it reaches a speed of 54 kmph, while train B accelerates uniformly at the rate of 0.6 meter per second square until it reaches a speed of 72 kmph and then travels at this speed. Determine when and where both will cross each other


Homework Equations


i don't know what equation to use........


The Attempt at a Solution


i tried equating there distance but it will just complicate the equation....
please help........i would like to know how to get the answer..
 

Answers and Replies

  • #2
tiny-tim
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hi herbgriffin! :wink:

start by writing out the two equations for the positions of the two trains at any time t (put the origin, x = 0, at A) …

what do you get? :smile:
 
  • #3
i will get train a will be 225 m at t=30s while train b is 333.33 m at t=33.33s. I don't know if this is right........
 
  • #4
tiny-tim
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no, write two equations

always write equations!
 
  • #5
x=15+[(1/2) (0.5)t^2] train A
x= 20+[(1/2) (0.6) t^2] train B
please correct me if i am wrong i am really confused
 
  • #6
tiny-tim
Science Advisor
Homework Helper
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hi herbgriffin! :smile:

(try using the X2 icon just above the Reply box :wink:)
x=15+[(1/2) (0.5)t^2] train A
x= 20+[(1/2) (0.6) t^2] train B
please correct me if i am wrong i am really confused

your 1/2 (0.5)t2 and 1/2 (0.6)t2 parts are correct,

but i don't understand where your 15 and 20 come from :confused:

also you haven't shown them travelling in opposite directions,

and you haven't dealt with the steady motion after each trains reaches its cruising speed
 

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