Calculating Distance of Runners from Flagpole When Paths Cross

[alexistheman]

Runner A is initially 5.6 km west of a flagpole
and is running with a constant velocity of
8.7 km/h due east. Runner B is initially 4.2
km east of the flagpole and is running with a
constant velocity of 7.4 km/h due west.

How far are the runners from the flagpole
when their paths cross? Answer in units of
km.


How do i even start this, I am stuck.

 

[Jebus_Chris]

Drawing the scenario is always a good place to start.
R1------------------------------F-------------------------R2
Now you're looking for when R1 and R2 pass each other. That means what?

 

[alexistheman]

displacement by chance?

 

[alexistheman]

Like i drew it out, but when i do i still don't know how to set it all up. I am so stumped. :(

 

[alexistheman]

I got .3 KM but it says its wrong.. ugh

 

[Jebus_Chris]

The runners will pass each other. This would happen after t hours. So that means that after t hours both runners will be at the same spot (not the same distance ran).
-Basically, at some time t, the two runners x position will be equal.

 

[indep]

8.7 km/h + 7.4 km/h = 4.7 km + 5.6 km

16.1 km/h = 9.8 km

t = 9.8 km / 16.1

t=.608695652

8.7 * .608695652 = 5.29565213

5.6 - 5.29565213 = .30434782

your answer is .30434782 buddy

 

[alexistheman]

Hm, confusing. lol. I set it up and got 5.29 but ugh wouldn't it be .31

 

[Jebus_Chris]

Hm, confusing. lol. I set it up and got 5.29 but ugh wouldn't it be .31

Why don't you post what you did.

 

[alexistheman]

Ugh it wanted the full number, thanks ~.~

 

[alexistheman]

it was operator and stupid website error lol

 

[indep]

happens..i had trouble on this one early tonight but i figured it out..

 

[alexistheman]

well thanks man, heh.

 

[indep]

no prob.