Newton's 2nd law
.
. Resultant force = mass × acceleration.
Method.
- Identify all forces on body.
- Find resultant (vector sum) in each direction.
- Apply in that direction.
Example. 4 kg on smooth surface, 20 N horizontal push. → → m/s².
With friction. Subtract friction from applied force.
On incline. Resolve weight along/perp to slope.
Cambridge tip. Always sketch with forces labelled. Mark scheme rewards diagram.
- in EACH direction.
- Use RESULTANT force.
- Sketch + label.