Mass vs Weight

 Mass is the amount of matter in an object, measured in kilograms (kg). It never changes based on your location. 

Weight is the gravitational force acting on that mass, measured in Newtons (N). Weight varies depending on the area's local gravitational force (e.g., you would weigh less on the Moon than on Earth).

Here are some specific differences in how they are defined, measured, and calculated:

The Core Differences Between Mass and Weight

Mass: 

Mass is a fundamental measure of the amount of matter (or material contained) in an object. It is a scalar quantity, meaning it has only size and magnitude, and it remains the same whether you are on Earth, the Moon, or floating in deep space. Additionally, mass measures an object's inertia (its resistance to change in motion), which is its resistance to being moved or accelerated.

Weight: 

Weight refers to the force exerted on a mass by gravity.
Because it is a force (vector quantity), it has both magnitude and direction (pulling downward toward the center of the planet).
Your weight will change if you travel to a location with stronger or weaker gravity, even though your mass never changes. That's why you are lighter on the moon.
Your weight on a mountaintop is lesser as you are farther from the Earth's gravitational force.

The Physics Formula for Gravity and Mass

In physics, weight and mass are linked by Newton's second law of motion (F = ma). 

For gravity, the formula is:

W = mg 

Where:

W is the Weight (in Newtons, N)

M is the Mass (in kilograms, kg)

G is the Acceleration due to Gravity 

On Earth, g is approximately 9.8 m/s². 

Therefore, an object with a mass of 10 kg has a weight of 98 N (10 kg × 9.8 m/s²)

How Do They Measure Mass or Weight

Measuring Mass: 

Use a pan balance or an electronic digital balance.
These tools measure the unknown mass of the object by comparing it to a known standard mass.

Measuring Weight: 

They use a spring balance.
The spring stretches based on the downward pull of the gravitational force acting on the object. 

Example:

Consider a person with a mass of 60 kg:

On Earth, the gravity is strong (9.8 m/s²), so their weight is (60 X 9.8), ie., 588 Newtons (N).

On the Moon, the gravity is only about 1.6 m/s² (roughly one-sixth as strong as Earth). Their mass is still 60 kg, but their weight drops to roughly 98 N from 588 N.

Rice Bag Example:

When you buy a 50 kg bag of rice, the label is actually showing you its mass, not its physical weight in Newtons. So, the weight can change when you travel to a place where the gravitational force is weak.

Even though everyday language uses the word "weight," science and commerce treat it differently.

In real life, Mass is the focus. The manufacturer tells you exactly how much physical rice (matter) is inside the bag.

 

The kilogram (kg) is strictly a unit of mass. If it were a true measurement of weight in physics, it would be labeled in Newtons (N), not in Kgs.

So, in daily life, "to weigh" simply means to put something on a scale.
Because Earth's gravity is relatively constant everywhere we shop, society uses the terms interchangeably.

What the Rice Bag Measures in Physics:

If you want to look at that 50 kg bag of rice through a strict physics lens, the two concepts split:

Its Mass is exactly 50 kg. This stays the same whether you buy the rice in New York, on top of Mount Everest, or on Mars.

Its True Weight is approximately 490 Newtons.
This is calculated by multiplying the mass (50 kg) by Earth's gravity (9.8 m/s²). It will weigh less on a mountaintop or on the Moon.

References:

https://byjus.com/physics/mass-and-weight

https://en.wikipedia.org/wiki/Mass_versus_weight

https://www.vedantu.com/physics/measurement-of-mass-weight