WEBVTT

1
00:00:00.000 --> 00:00:09.416
Here is the problem: A crate presses on the floor with a normal force of 250 N. If μ equals 0.6, what is the friction force?

2
00:00:09.866 --> 00:00:14.638
Use the friction formula, rearranged for the unknown, in SI units.

3
00:00:15.438 --> 00:00:16.738
Formula: friction.

4
00:00:17.188 --> 00:00:19.139
Substitute the known values.

5
00:00:19.939 --> 00:00:23.991
So the answer is friction force f equals 150 N.

6
00:00:24.441 --> 00:00:37.688
Kinetic friction opposes sliding with magnitude f equals μₖN; static friction can take any value up to μₛN. On a level surface with no other vertical forces, the normal force equals the weight mg.

7
00:00:38.488 --> 00:00:44.142
Substituted every value back into the formula: both sides agree, which checks out.