# Homework Help: LearningPhysics one last runner problem

1. Sep 13, 2007

### anglum

1. The problem statement, all variables and given/known data
Runner A is initially 6.0km west of a flagpole and is running with a constant velocity of 8.4km/h east. Runner B is initially 4.3km east of flagpole and is running with a constant velocity of 7.1km/h west

how far are the runners from the flagpole when their paths cross?

3. The attempt at a solution

so again the time for both are the same and the distance apart is 10.3 km
do i solve for t since t is equal for both runners?

2. Sep 13, 2007

### learningphysics

Yes, t is equal... how do the distances the two runners travel relate?

3. Sep 13, 2007

### anglum

well since the time is equal then wouldnt the distance of runner A be 1.18309 times more than runner B???

4. Sep 13, 2007

### learningphysics

Yes, but you don't really need that relationship... how does the 10.3km come into play here?

5. Sep 13, 2007

### anglum

im not sure how that comes into play since its where do they intersect

6. Sep 13, 2007

### learningphysics

draw a sketch... they start at 10.3km apart... they run towards each other... draw a line for the path one runner travels... draw a line for the other...

what is the relationship between the length of the two lines?

7. Sep 13, 2007

### anglum

i see that they intersect i jsut dont know what formula or what i try and solve for to get this problem

8. Sep 13, 2007

### learningphysics

Well, I was getting at... the distance travelled by one runner + distance travelled by the other = 10.3 km

9. Sep 13, 2007

### anglum

ahhhhh damn i knew that ... i thought u meant something more complex... its gettin late here and im bucklin down to finsih this last one

10. Sep 13, 2007

### anglum

so if the Time is equal and the Distance is D of 1 + D of 2 = 10.3 how do i solve for that?

11. Sep 13, 2007

### anglum

do i get 8.4t + 7.1t = 10.3 km?

which give me a time of intersect at .6645 hours?

12. Sep 13, 2007

### learningphysics

yup. how far are they from the flagpole.

13. Sep 13, 2007

### anglum

so after that time runner A has gone 5.581935484 km and he was initially 6km away

so he is now .4180645161 km away from the pole

14. Sep 13, 2007

### anglum

AWESOME THAT WAS CORRECT

YOU ARE THE MAN AND A SAVIOR.... this should be all my problems until next week... i was workin ahead to avoid them over the weekend

15. Sep 13, 2007

### learningphysics

cool. no prob.