Trains heading toward each other

  • Thread starter chawki
  • Start date
  • #1
506
0

Homework Statement


One train runs from A to B at 105 miles per hour, the other runs from B to A at 85 miles per hour.

Homework Equations


How far apart were the two trains 30 minutes prior to their crossing?

The Attempt at a Solution


if the distance between them is x, i can find the time when they cross each other.
t=x/(190)
 

Answers and Replies

  • #2
kuruman
Science Advisor
Homework Helper
Insights Author
Gold Member
10,363
3,462

Homework Statement


One train runs from A to B at 105 miles per hour, the other runs from B to A at 85 miles per hour.

Homework Equations


How far apart were the two trains 30 minutes prior to their crossing?

The Attempt at a Solution


if the distance between them is x, i can find the time when they cross each other.
t=x/(190)
How far apart are the trains to begin with?
 
  • #3
506
0
They didn't say
 
  • #4
supratim1
Gold Member
279
1
30 mins * relative velocity = x. wont that be the answer?
 
  • #6
supratim1
Gold Member
279
1
so initial distance is not required!
 
  • #7
kuruman
Science Advisor
Homework Helper
Insights Author
Gold Member
10,363
3,462
so initial distance is not required!

It is not. I misread the problem at first.
 
  • #8
506
0
t-0.5=x/190 ?
 
  • #9
kuruman
Science Advisor
Homework Helper
Insights Author
Gold Member
10,363
3,462
supratim1 has already posted the method of calculation above (#4). Be sure to have a consistent system of units.
 
  • #10
506
0
yeah but i don't understand it
i don't know about the relative velocity
 
  • #12
506
0
i still don't get it...
isn't there another method more simple?
 
  • #13
kuruman
Science Advisor
Homework Helper
Insights Author
Gold Member
10,363
3,462
i still don't get it...
isn't there another method more simple?
There isn't. This is a problem about relative velocity and you have to understand what that means. Here we go. Please think about and answer the following two questions.

Question 1
Suppose you are in a car traveling at 60 miles per hour going North. You look out the window and you see a road sign. Would you say that the road sign is moving? If so, how fast and in what direction?

Question 2
Suppose you are in a car traveling at 60 miles per hour going North. You look out the window and you see a car going in the opposite direction (South). The speedometer of that car reads 50 miles per hour. Would you say that that car is moving? If so, how fast and in what direction?
 

Related Threads on Trains heading toward each other

  • Last Post
Replies
11
Views
15K
Replies
1
Views
2K
  • Last Post
Replies
1
Views
5K
  • Last Post
Replies
7
Views
8K
Replies
24
Views
1K
Replies
2
Views
4K
Replies
15
Views
2K
  • Last Post
Replies
17
Views
2K
Replies
1
Views
1K
Top