# What Happened When I Gave Them the Answers

Reblogging today’s 180 blog post to Action-Reaction in order to try to get more feedback from folks. Click through to read more and leave comments over there. Thanks!

[TL;DR – Not as much as I had hoped.]

College-Prep Physics: Students came to class with the following question completed for homework:

You are on a sleigh ride in Central Park one brisk winter evening. The mass of the sleigh with everyone in it is 250 kg, and the horses are pulling the sled with a combined horizontal force of 500 N. The sled moves at a constant speed of 3.33 m/s.
(a) What is the force of kinetic friction on the sleigh?
(b) What is the coefficient of kinetic friction between the sleigh and the ground?

I asked everyone to whiteboard their answers. I heard some students say they didn’t get it. Several other students came up to me — worksheet in hand — to ask if their answer was right.

“I’m going to give you the answers,” I said. “Here they are.”

“Now on your whiteboards, I want…

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