Slowly walking in the rain or running fast?

[saravanan13]

Who will get more wet?
The one who is slowly walking in the rain or the who is running fast?
What is the physics behind it?

Thanks in well advance

 

[pallidin]

Well, that depends.
Assume this scenario:
Open field, 1-mile wide in all directions and raining hard...
You and your brother are at the same spot.
You take-off running while your brother instead decides to just slowly walk in the same direction.
In 10 seconds, who get more wet?

 

[DaveC426913]

There's a http://www.youtube.com/watch?v=eEq_qKgtW6Y" for that...

A nonintuitive result.

 

[JDługosz]

I did not like the MB episode.

Consider: someone moving at very high speed, fast enough to call it infinity. The person will bore out a rectangle from point A to point B horizontally and his own height vertically. All the raindrops in that rectangle will wind up on his front.

Someone else moving so slowly he might as well be zero. It would take a very very long time to get to B. The rain keeps coming down and landing on his head. He would continue getting wet without limit.

In general, think of a diagonal line from A to the point above B where the raindrop is initially that will hit the ground when the person gets to B. Draw another diagonal parallel to that, for the person's head. The enclosed area is all the rain he will hit.

The infinite speed case is the smallest area. The area increases as the person moves slower.

===

Pallidin, that's a different question. Suppose we are equally wet after 10 seconds, but I'm at the door while brother is still getting rained on.

 

[Doc Al]

Here's a thread from a few years ago on this topic: https://www.physicsforums.com/showthread.php?t=126785