Define velocity and acceleration, and state their SI units.

**The reasoning** This isn't a multiple-choice question — it's asking you to **define and explain** two fundamental physics concepts: **Velocity** is the rate of change of displacement with time. It tells you how fast something is moving *and in what direction*. Formula: **v = Δs/Δt** (displacement ÷ time). SI unit: **metres per second (m/s)**. **Acceleration** is the rate of change of velocity with time. It tells you how quickly velocity itself is changing. Formula: **a = Δv/Δt** (change in velocity ÷ time). SI unit: **metres per second squared (m/s²)**. Notice both are *vector quantities* — direction matters! **Why this format matters** WAEC and JAMB often mix MCQs with "theory" questions requiring definitions. Students sometimes panic and write vague answers like "velocity is speed" (wrong — speed has no direction) or forget the SI units entirely. Always state the definition clearly, then add the unit. **Quick takeaway** Velocity = displacement per time (m/s); Acceleration = velocity change per time (m/s²) — both need direction to be complete.