Apparent Weight Summary Table
| Lift Condition | Acceleration | Apparent Weight W' | Feel |
|---|
| At rest or constant velocity | a = 0 | mg | Normal |
| Accelerating upward | a ↑ | m(g + a) > mg | Heavier |
| Accelerating downward | a ↓ | m(g − a) < mg | Lighter |
| Free fall | a = g ↓ | 0 | Weightlessness |
Friction Comparison Table
| Property | Static (fs) | Kinetic (fk) | Rolling (fr) |
|---|
| Formula | 0 to μ_s N | μ_k N | μ_r N |
| Self-adjusting | YES | NO | NO |
| Coefficient order | μ_s (largest) | μ_k (medium) | μ_r (smallest) |
| When active | Before motion | During sliding | During rolling |
SVG: Friction Force vs Applied Force
Applied Force →
Friction Force →
μ_s N (Limiting)
μ_k N (Kinetic, constant)
A
Static friction (rises with F)
Kinetic friction (constant)
Point A: Motion Begins
The graph shows that static friction rises linearly with applied force (self-adjusting) until it reaches μ_s N (limiting friction). At point A, motion begins, friction drops to the lower constant value μ_k N (kinetic friction), and remains constant regardless of further increase in applied force.
Centripetal Force Sources Summary
| Scenario | What Provides Fc |
|---|
| Car on level road | Friction (f = μN) |
| Car on banked road (no friction) | Horizontal component of N |
| Stone on string (horizontal circle) | Tension T in string |
| Satellite in orbit | Gravitational force mg |
| Roller coaster at top of loop | Weight mg + Normal force N |
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