Mass and weight are two terms that people often mix up, but they mean different things in science.

1. Mass:

   • What it is: Mass is how much stuff, or matter, is in an object.
   • How we measure it: We use kilograms (kg) to measure mass.
   • Key point: Mass doesn’t change, no matter where the object is.
   • Example: If something has a mass of 10 kg, it will still weigh 10 kg whether on Earth or the Moon.

2. Weight:

   • What it is: Weight is the force that gravity pulls on an object.
   • How we measure it: We use newtons (N) to measure weight.
   • How to calculate it: You can find weight using the formula (W = mg). Here, (g) is the pull of gravity, which is about (9.81 , \text{m/s}^2) on Earth.
   • Example: An object that has a mass of 10 kg weighs (W = 10 , \text{kg} \times 9.81 , \text{m/s}^2 = 98.1 , \text{N}) when it’s on Earth.

Why It Matters in Physics: Knowing the difference between mass and weight is really important. It helps us figure out how gravity works and how things move, which are key ideas in Newton's laws of motion.