Day 34: A Frictionless Wall


Today a student asked, “Could you ever hold a book against a frictionless wall if you just pushed hard enough?”

So I quickly tried to simulate a frictionless wall using a single dynamics cart, holding it against the wall with my hand. Didn’t work. “Friction between my hand and the cart held the cart in place” I suddenly realized.

So then I rigged two carts as pictured in order to simulate no friction on either side of the cart. Worked perfectly! There was no way to keep the carts from sliding to the floor.

A great demo to show the independence of horizontal and vertical forces.


About Frank Noschese

HS Physics Teacher constantly questioning my teaching.

2 responses to “Day 34: A Frictionless Wall”

  1. John says :

    I tried this today with a kid, and it’s even more awesome if you put the book up against the wall, and push with the carts. It shows that the carts can’t be exerting a frictional force upward, so the wall must be, which is a great lead in to your awesome demo.

Trackbacks / Pingbacks

  1. Day 33: Why Doesn’t the Book Fall? | Noschese 180 - October 31, 2013

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