Mass and weight are important ideas in physics that help us understand how things move. Knowing the difference between them is key to learning about motion.

Mass:

• Mass tells us how much stuff is in an object.
• It is measured in kilograms (kg) and does not change no matter where you are.
• For example, a 1 kg object will still weigh 1 kg whether it is on Earth, the Moon, or in space.

Weight:

• Weight is the force that pulls an object down because of gravity.
• It is measured in newtons (N) and can change based on how strong gravity is.
• You can find weight using this formula: $$W = m \cdot g$$ Here, $W$ is weight, $m$ is mass, and $g$ is the pull of gravity (about $9.81 \, \text{m/s}^2$ on Earth).
• For example:
  • An object with a mass of 10 kg weighs about $10 \times 9.81 = 98.1 \, \text{N}$ on Earth.

How They Affect Force and Motion:

1. Newton’s Second Law of Motion:

   • This law says that force equals mass times acceleration ($F = m \cdot a$).
   • If an object has more mass, it needs more force to move it the same way as a lighter object.

2. Inertia:

   • Mass helps us understand inertia, which is how much an object resists changes in its movement.
   • A heavier object needs more force to speed up than a lighter object.

3. Gravitational Force:

   • Weight changes how objects connect with each other through gravity.
   • For example, if you double the mass of an object, you also double its weight, which means it pulls harder on other objects.

In short, mass and weight are both very important for understanding how forces work and how things move around us.