What is Mass?
✅ Definition:
Mass is the amount of matter in an object.
It tells us how much "stuff" (material or substance) the object contains and how resistant it is to changes in motion.
📌 Mass is NOT the same as weight — mass stays the same everywhere, but weight can change depending on gravity.
📏 Units of Mass:
| Unit Name | Symbol |
|---|---|
| Kilogram | kg |
| Gram | g |
| Tonne (Metric Ton) | t |
🔹 The SI unit (international standard) for mass is the kilogram (kg).
⚠️ Mass vs. Weight:
| Mass | Weight |
|---|---|
| Amount of matter | Gravitational force acting on the mass |
| Same everywhere (Earth, Moon) | Changes with gravity (less on the Moon) |
| Measured in kg | Measured in Newtons (N) |
🧪 Example:
You may have a mass of 70 kg on Earth and the Moon.
But your weight on the Moon is about 1/6th of your weight on Earth because the Moon’s gravity is weaker.
🔬 Why is Mass Important?
-
In physics, it helps us understand motion, inertia, and force
-
In chemistry, it’s used in equations and reactions
-
In space science, it helps calculate gravitational pull and orbits
-
In engineering, it affects design, safety, and load limits
📘 Related Formulas:
-
F = m × a (Force = Mass × Acceleration)
-
Density = Mass / Volume → ρ = m / V
-
E = mc² (Einstein’s formula: Energy and Mass are interchangeable)
🧠 Fun Facts:
-
Mass does not change, even in space
-
Light (photons) has no rest mass
-
The Hydrogen atom has the smallest mass among elements
-
Mass and energy can transform into one another (as in nuclear reactions)
📌 Summary:
| Concept | Explanation |
|---|---|
| What is Mass? | The amount of matter in an object |
| Measured in | Kilograms (kg), grams (g), tonnes (t) |
| Mass ≠ Weight | Mass stays the same; weight depends on gravity |
| Why it matters | Used in physics, chemistry, engineering, space science |