Solve a problem

FrictionPhysicsHigh schoolabout 0:44

A crate presses on the floor with a normal force of 55 N. If μ = 0.4, what is the friction force?: animated lesson

A narrated, step-by-step friction video lesson with captions. Final answer: friction force f = 22 N.

SpeedLanguage

Video with a synthetic English voice and captions. Pick another language for subtitles in that language, or open the interactive version.

Video narrated by a synthetic voice (Piper TTS, en_US-ljspeech-high voice (LJ Speech dataset, public domain)); the steps come from our maths engine and the answer was checked independently. Download MP4 (0.3 MB) · Captions (WebVTT)

Steps on screen

1. The problem
Worked example
A crate presses on the floor with a normal force of 55 N. If μ = 0.4, what is the friction force?
2. Step by step
1. $f = \mu N$
  Formula: friction
2. $f = (0.4)\cdot (55\ \text{N}) = 22\ \text{N}$
  Substitute the known values
3. The answer
$\text{friction force f = 22 N}$
friction force f = 22 N
4. Check
- Substituted every value back into the formula: both sides agree ✓

Transcript

The problem. Here is the problem: A crate presses on the floor with a normal force of 55 N. If μ equals 0.4, what is the friction force? Use the friction formula, rearranged for the unknown, in SI units.

Step by step. Formula: friction. Substitute the known values.

The answer. So the answer is friction force f equals 22 N. 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.

Check. Substituted every value back into the formula: both sides agree, which checks out.

About friction

Find friction forces from the normal force and the coefficient of friction.

A crate presses on the floor with a normal force of 55 N.…