Math Is Fun Forum

paulb203

Member

Registered: 2023-02-24

Posts: 287

Friction and Drag

From a physics website;

"Every time the surface of a solid collides with an air molecule, there is force acting on the solid slowing it down"

My question;

What if the air molecule collides with the BACK of the solid? What if a man walking down the street on a windy day is struck on the back by molecules of air; wouldn't this, if anything, speed him up?

---

Prioritise. Persevere. No pain, no gain.

Bob

Administrator

Registered: 2010-06-20

Posts: 10,598

Re: Friction and Drag

I've definitely been blown along by a wind on my back.  So you're correct.

The website should have said  "Every time the surface of a solid collides with an air molecule, there is force acting on the solid.  If the solid is trying to push through the air, this force will slow it down."

Bob

Not everything on the internet is true.

Physicists sometimes get things wrong; eg. saying there's a thing called centrifugal force.

---

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob