Laws of Motion — Class 11 ISC Physics revision notes
A 7-page visual revision sheet for Laws of Motion, written for Class 11 ISC Physics. Formulas, diagrams and the traps that cost marks, laid out to be read the night before rather than the term before. Free, and it opens inside CapCompass.
Page 1 as PDF
Laws of Motion in one look
three laws, one free body diagram, and the two forces that turn a corner
The three laws, and what each one is for
- first law: no net force, no change in motion; it defines force and inertia
- second law: F = dp/dt; for constant mass F = ma, a vector equation
- third law: equal and opposite, on different bodies, so they never cancel
- the syllabus derives the third law from conservation of momentum
F = ma is the special case, not the law
- the law is F = dp/dt; the v dm/dt term vanishes for constant mass
- near c, mass is not constant: m = m_0/√1-v^2/c^2, so F = ma is classical
- impulse Ft = Δ p: a longer collision means a smaller force
- quoting F = ma as the law loses marks: call it the special case
The quantities, and their units
| Quantity | Definition | SI unit | Dimensions |
|---|---|---|---|
| momentum p | mv | kg m s^-1 | [M L T^-1] |
| force F | dp/dt | newton, N | [M L T^-2] |
| impulse | F t, equals delta p | N s | [M L T^-1] |
| weight | mg | newton, N | [M L T^-2] |
Page 1 of 7. The full sheet, all 7 pages, opens free in the app.
What this Laws of Motion sheet covers
- The three laws, and what each one is for
- F = ma is the special case, not the law
- The quantities, and their units
- Action and reaction
- Conservation of linear momentum
- Equilibrium of a particle
- Solving any mechanics problem, in this order
- Isolate
- Draw
- Resolve
- Solve
- Free body diagrams, and connected bodies
- Wedges and ladders
- What a balance reads
- angle of repose
- angle of friction
- Friction, and the two regimes
- The friction results a question will want
- Friction on a slope
- Circular motion needs a force, not a new one
- Turning a corner, three cases
- Pseudo forces
- Pseudo force in a lift and on a giant wheel
- Changing mass: rockets, chains, sand
- Traps that cost marks
- Tricks that save time
How CapCompass uses this sheet
These notes are not a standalone PDF. CapCompass plans Physics chapter by chapter against your real exam dates and free hours, and when the plan reaches Laws of Motion the sheet opens inside the study block itself — at the page covering the sub-topic that block is on, with the timer still running. Revision arrives at the moment the plan says revise, instead of having to be gone looking for.