Physics · Grades 10–12
Kinetic friction model
This is sliding friction with the stated coefficient, not a universal rule for static friction.
Rule and assumptions
This is sliding friction with the stated coefficient, not a universal rule for static friction.
Fₖ = μₖN
Worked examples
A sliding block has normal force 17 N and kinetic friction coefficient 0.4. Find the friction-force magnitude in this model. Round to 3 decimal places if needed. Answer in N.
Fₖ = μₖN 0.4 × 17 = 6.8
6.8 N
A sliding block has normal force 132 N and kinetic friction coefficient 0.6. Find the friction-force magnitude in this model. Round to 3 decimal places if needed. Answer in N.
Fₖ = μₖN 0.6 × 132 = 79.2
79.2 N
Try two questions
A sliding block has normal force 146 N and kinetic friction coefficient 0.8. Find the friction-force magnitude in this model. Round to 3 decimal places if needed. Answer in N.
A sliding block has normal force 51 N and kinetic friction coefficient 0.4. Find the friction-force magnitude in this model. Round to 3 decimal places if needed. Answer in N.
Answers and reasoning
Answers and marking notes
- 116.8 N
Fₖ = μₖN 0.8 × 146 = 116.8
- 20.4 N
Fₖ = μₖN 0.4 × 51 = 20.4
Further reading and review references
These are reference links, not copied exercises, institutional endorsement or proof of independent review.
Learning preview · independent educational and translation review required. Suggested grades are not official curriculum alignment.