Skip to content
Dabour HubLEARN · PRACTICE · EXPLORESign inStudent

2.6.5Force and Translational Dynamics

Slipping and Sliding — AP PHYSICS 1 Revision Notes & Topical Questions

5 min read 10 parts Lesson 27 of 36 1 quiz

📚 AP PHYSICS 1 Hub / Topical Revision
🩺
100% Curriculum Specification Match Lesson Doctor Verified
The only platform with 100% curriculum specification match and verified interactive question banks.
0%read
Lesson summary

2.6.5 Slipping and Sliding — AP PHYSICS 1 notes: Analyse the change from static to kinetic friction, interpret friction graphs and handle stacked or accelerating objects.Sliding — two surfaces in contact move relative to each other and kinetic friction applies.Slipping — a specia…

  • At the limit
  • Increasing applied force
  • Verge of slipping
  • After slipping
  • Force-sensor record
  • No slipping

Section 1 of 10Sliding and slipping

Sliding
  • Sliding two surfaces in contact move relative to each other and kinetic friction applies.
Slipping
  • Slipping a special case in which an object that normally rolls does not roll.
  • A braking bike wheel slides over the ground and kinetic friction acts.
  • The centre of mass then moves faster than the contact point with the ground.
Rolling
  • Rolling static friction applies to a rolling object.

Section 2 of 10Maximum static friction

Adaptive
  • Adaptive static friction takes the value and direction needed to prevent slipping.
Maximum
  • Ff,s,max = μsFN, reached at the point of slipping.
At the limit
  • At the limit it equals the applied force in size and is opposite in direction.

Section 3 of 10From sticking to sliding

Increasing applied force
  • Increasing applied force static friction grows to match it, so the object stays at rest.
Verge of slipping
  • Verge of slipping applied force equals μsFN.
After slipping
  • After slipping friction drops to the usually smaller μkFN and the object accelerates (the lurch).

Section 4 of 10Friction–force graph

RegionShapeValue
StaticStraight line, gradient 1, through originFriction equals applied force up to μsFN
KineticHorizontal lineμkFN, whatever the applied force
Force-sensor record
  • Force-sensor record force rises, peaks, then falls to a constant level while the block slides steadily.
Use
  • Use with FN known, the peak gives μs and the plateau gives μk.

Section 5 of 10Stacked blocks and accelerating surfaces

Stacked blocks and accelerating surfaces
Top block
  • Top block its only horizontal force is static friction from the lower block, fs = mtopa.
No slipping
  • No slipping requires a ≤ μsg, so amax = μsg.
Maximum pull on the stack
  • Fmax = (mtop + mbottom)μsg on a frictionless table.
Beyond the limit
  • Beyond the limit the top block slips backward relative to the bottom one and kinetic friction acts.
Cargo on a truck
  • Cargo on a truck slides when the needed acceleration exceeds μsg.

Section 6 of 10Direction and energy when slipping

Direction
  • Direction kinetic friction opposes the relative sliding of the surfaces.
  • A top block slipping backward still feels friction forward; the bottom block feels it backward.
Third-law pair
  • Third-law pair friction forces on the two blocks are equal and opposite, but accelerations differ with mass.
Energy
  • Energy sticking dissipates nothing;
    • sliding produces thermal energy equal to fk times the relative sliding distance.

Section 7 of 10Sliding to a stop

Deceleration
  • Deceleration a launched block decelerates at μkg.
Distance and time
  • Distance and time d = v2 / (2μkg) and t = v / (μkg).
  • Halving μk doubles the stopping distance.
Thermal energy
  • Thermal energy equals the initial kinetic energy ½mv2, which equals fkd.
Three regimes
  • Three regimes at rest below the limit, on the verge of slipping, or sliding;
    • the wording of a problem selects which friction equation to use.

Section 8 of 10More from the specification

1Transition from static to sliding friction
  • Transition from static to sliding friction exceeding threshold static grip causes sudden slipping, providing a mechanical means to study dynamic traction.
2Threshold
  • The output value at which a switching circuit changes state.
3Velocity
  • Rate of change of displacement.
4Normal reaction
  • The contact force perpendicular to a surface.
5Reaction force
  • Force from a support pushing up on an object.
6Constant velocity
  • Zero acceleration.

Section 9 of 10Key terms

TermMeaning
SlippingStart of relative sliding between surfaces.
Limiting frictionMaximum static friction.
Relative motionMotion of one object measured from another.
PlateauLevel part of a graph where the value is constant.
StackObjects resting one on another.

Section 10 of 10Exam technique

1
Believing friction stays at the maximum static value once sliding begins.
2
Forgetting that μs is normally greater than μk.
3
Assuming the top block slips whenever the table accelerates — it slips only if the required acceleration exceeds μsg.
4
Choosing the wrong friction direction on the top block of an accelerating stack.
5
Treating the force graph as a straight line after slipping.

Last updated: