Calculating Distance and Time for Two Cars on a One-Dimensional Road

[Questions999]

An automobile which travels with the constant speed 20 m/s passes in a section in the moment t=0s and 5 seconds later in the same section passes another automobile which travles with the speed of 30 m/s in the same direction.a) Find when the second car meets the first one.
My solution : x1=x2 20t=30(t-5) and here we find t=15 seconds.b) Whats the distance between the cars since the section until they meet? How to do this one? Just give me an idea..

 

[tiny-tim]

Hi Elaia06!

hmm …

ahh! , i think you mean …​

An automobile which travels with the constant speed 20 m/s passes a line at time t=0s and 5 seconds later another automobile which travels with the speed of 30 m/s in the same direction passes the same line.
a) Find when the second car meets the first one.
My solution : x1=x2 20t=30(t-5) and here we find t=15 seconds.b) Whats the distance past the line when they meet?

your equations should be …
x₁ = 20t
x₂ = 30(t-5)
x₁ = x₂

you already have t = 15,

so x₁ = x₂ = … ? ​

 

[Questions999]

I did it this way, but my teacher said it was not correct Now I logged in physicsforum and I see we have the same opinion :S Even the other students had done it this way.Whatever,thank you :)

 

[tiny-tim]

Hi Elaia06!

Please remember that I rewrote the question so that it fitted your solution!

Perhaps the question means something different?

 

[Questions999]

So the distance question means " The two cars,since they pass the line have a distance.They keep this distance until they meet.Find the distance.This is basically what I did,found that distance.

 

[tiny-tim]

" The two cars,since they pass the line have a distance.They keep this distance until they meet.Find the distance.

sorry, but that doesn't make any sense

(how can they keep the distance if the distance is getting smaller?)

 

[Questions999]

Thats what it says in my book,literally.I am not english and the book I work with is translated poorly ..Whatever,thank you anyway..