Why does your weight change but not your mass?

Author: Dr. Norma Kirlin MD  |  Last update: Wednesday, April 9, 2025

Mass is the total amount of matter, or "stuff," in an object. Weight is the force of gravity on an object. Mass always stays the same, but weight can change depending on how much gravity is acting upon an object.

Can you change your weight without changing your mass?

Weight: The weight of an object is the product of its mass and the acceleration due to the force of gravity, W = m ⋅ g . The weight of an object can change even if the mass does not if the acceleration due to gravity changes.

Does your mass change when your weight changes?

Remember, even if you weigh less because of a change in gravity's force on your body, your body's mass is still the same. As your body grows, you will have more mass, which also means you will weigh more. That's because when you're on the earth, the amount of gravity that pulls on you stays the same.

Can a body have a weight but no mass?

Therefore, a body cannot have any weight without any mass.

Why does mass do not change?

Mass does not change in space because it is an intrinsic property measuring the amount of matter in an object, and it remains constant regardless of location. Weight, on the other hand, can vary based on gravitational forces. Hence, while weight differs on Earth and the Moon, an object's mass stays the same throughout.

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Why does weight change but not mass?

Mass and weight may seem like the same thing, but in fact these two measurements are very different. Mass is the total amount of matter, or "stuff," in an object. Weight is the force of gravity on an object. Mass always stays the same, but weight can change depending on how much gravity is acting upon an object.

Why can't mass change?

Matter can change form through physical and chemical changes, but through any of these changes matter is conserved. The same amount of matter exists before and after the change—none is created or destroyed. This concept is called the Law of Conservation of Mass.

Why does a body have mass but no weight?

Yes, mass of a body os constant wherever it is taken. But weight of body, W=mg. The weight will be zero where g=0 e.g. At the centre of earth.

Can I weigh a lot but not look fat?

A few people have high BMIs but don't have much body fat. Their muscle tissue pushes up their weight. Kahan points to very muscular people, like football players or body builders. “Their BMI shows up pretty high, and yet their body fat is actually pretty low," Kahan says.

Can you gain mass while losing weight?

As with the start of any new year, many of us set fitness goals for 2025. Most people focus on losing weight or gaining muscle -- but did you know it's possible to achieve both at the same time? This popular concept is called body recomposition, and it requires rather meticulous planning for it to work properly.

Is my weight actually my mass?

Your mass is 40 kilograms no matter where you are. But your weight differs from place to place because of differences in how hard gravity at each site pulls on you. On Earth's surface, 1 kilogram of mass is equivalent to 2.2 pounds of weight. So your 40-kilogram mass on Earth would weigh 40 x 2.2 — or 88 pounds.

Can a mass cause weight gain?

Some tumours can cause an increase in weight, perhaps because of their size, and fluid retention or constipation.

Can the weight of a body be but not the mass?

Hence the weight of the body can be zero. Now as we know that the mass of any body does not depend on any parameter it is dependent only on the object i.e. body because mass is an intrinsic property. So the mass of a body can never be zero.

What are 10 differences between mass and weight?

Key Differences Between Mass and Weight

Mass is the amount of matter in a body. Weight is the force exerted on an object due to gravity. Mass measures inertia, which is the resistance to changes in motion. Weight measures force, which is the product of mass and gravity.

Why do I look slimmer but weigh more?

So even though you may be losing fat, you're gaining muscle. You might feel slimmer, even as the number on the scale rises. “The scale doesn't tell the entire story,” said exercise physiologist Christopher Mohr, PhD, RD. “Since muscle and fat take up different volume, they look very different on the body.”

Why does my weight change every time I step on the scale?

What it likely is: a normal fluctuation caused by fluid level changes, or just a plain old inaccurate home scale. Try moving the scale to a different area in the bathroom or house and you'll get a slightly different number each time you step on it.

What has size and shape but no weight?

Answer: Anything in zero-gravity can have a certain size, shape but will be weightless.

Is there a difference between body mass and body weight?

Your body weight is simply your body's total mass. Body composition is what your weight is made of—muscle, bone, water, and fat.

Is it possible for an object to lose weight but not mass?

While the weight of an object varies in proportion to the strength of the gravitational field, its mass is constant, as long as no energy or matter is added to the object. For example, although a satellite in orbit (essentially a free-fall) is "weightless", it still retains its mass and inertia.

How do you get mass?

The equation variables can be algebraically rearranged to solve for mass so that m=F/a. Thus, if the amount of force applied to an object and its rate of acceleration is known, the mass of the object can be calculated by dividing the force by the acceleration.

What is the formula for weight?

To calculate the weight, use the following general formula: W = mg. Here, “W” is the weight of the object, “m” is the mass of the object, and “g” is the acceleration due to gravity.

What can change mass?

Force can change mass in two senses: First: force can change the mass of an object by speeding it up or slowing it down as measured by an observer in an inertial frame. An inertial frame is one which does not accelerate.

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