Solve Relative Motion Problem: Moving Sidewalk Airport Terminal

[Gold3nlily]

An airport terminal has a moving sidewalk to speed passengers through a long corridor. Larry does not use the moving sidewalk; he takes 140 s to walk through the corridor. Curly, who simply stands on the moving sidewalk, covers the same distance in 65 s. Moe boards the sidewalk and walks along it. How long does Moe take to move through the corridor? Assume that Larry and Moe walk at the same speed.


VAC = VAB + VBC
d=vt



This problem is from the relative motion section of my textbook, but it doesn't specify the reference point. I am assuming the reference point (RP) is the ground and that it is in front of the moving side walk.

RP --------------------------------------------> (moving sidewalk)

all three trips move the same amount of distance (d).
Vwalk = d/140 sec
Vride = d/65 sec
d=vt (but d is same so...)
Vw(140)=Vr(65) ---> so still have two variables...?!

I also tried:
Vwg= d/140 sec (g = ground)
Vrg = d/65 sec
Vwr ... doesn't work. Vrg would have to become Vgr.

I am totally lost on this problem. It is embarrassing. Can someone please walk me through it with hints? I would really appreciate it.

I would also be grateful for any general advice about how to solve problems that seem under represented by the textbook or advice about how to handle stress when I cannot figure out a problem on my own. Some of these physics problems really blow my academic confidence and I am only in physics 1! I need to learn how to think more like a physicist.

 

[lanedance]

i think you were almost there... the trick is you don't have to solve for the intermediate speeds, just moes final time

Vw = d/140
Vr = d/65

moe's speed is:
Vm = d/140 + d/65

then moe takes
tm = d/Vm

 

[Gold3nlily]

Wow! Thank you very much.

I had set up the equation: (d/t3) = (d/140) + (d/65) on my papers so many times but I was too busy gawking at the fact that I have two missing variables to move forward.

When you broke this problem up into these two steps:

"moe's speed is:
Vm = d/140 + d/65

then moe takes
tm = d/Vm "

It made so much sense.

I hope I can learn to apply this method to any other problems I have trouble with later. THank you again for your help. I really really appreciate it.