Cue Column:

• When to define signs?
• What about g?
• Common error?

Notes: Step 1: Choose positive direction BEFORE writing any equation. Standard: Upward = +ve, Rightward = +ve. g is always 9.8 m/$s^2$ in MAGNITUDE. In equations, use a = -g if upward is positive, a = +g if downward is positive.

Common Error: Mixing sign conventions mid-problem. If you choose upward = positive, then for a ball thrown up: u = +20 m/s, a = -10 m/$s^2$, and displacement below launch point is NEGATIVE.

Summary: Define signs once, apply everywhere. Never change mid-solution.