Which of these is a vector quantity?

**The reasoning** A **vector quantity** has both **magnitude** (size) and **direction**. A **scalar quantity** only has magnitude. Let's check each option: - **Mass**: Just a number (e.g., 5 kg). No direction involved. ❌ Scalar - **Speed**: Just how fast (e.g., 20 m/s). Doesn't tell you *where* you're going. ❌ Scalar - **Velocity**: Speed + direction (e.g., 20 m/s northward). ✅ **Vector** - **Time**: Just duration (e.g., 10 seconds). No direction. ❌ Scalar **Velocity** = speed with a compass. That direction component makes it a vector. --- **Why the wrong options tempt you** Students often confuse **speed** and **velocity** because they seem similar. But speed is "how fast," while velocity is "how fast *and which way*." Mass and time clearly don't involve direction, so they're easier to eliminate once you remember the rule. --- **Quick takeaway** **If it needs an arrow to show direction (like velocity, force, displacement), it's a vector; if it's just a number, it's a scalar.**