Newton’s Second Law
Net force equals mass times acceleration.
F = ma
1What it means
Force is what changes motion. For the same force, a heavier object (more mass) accelerates less. The SI unit of force is the newton (N).
2Variables
| Symbol | Meaning |
|---|---|
| F | Net force (newtons, N) |
| m | Mass (kilograms, kg) |
| a | Acceleration (m/s²) |
3Worked examples
Example 1 Worked solution
Q. What force accelerates a 1,200 kg car at 3 m/s²?
- F = m × a = 1200 × 3.
✓ F = 3,600 N
4Where it's used
- ✦Vehicle braking and acceleration design.
- ✦Rocket and lift (elevator) force problems.
5Tips & common mistakes
- !F is the net (resultant) force — add up all forces first.
- !1 N = 1 kg·m/s².