What is mass and Weight ? Differene Between Mass and Weight

A man is seen pushing a cart that features a scale, demonstrating the measurement of mass in everyday life.

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Not sure how mass and weight are different? This guide will make it easy to understand.

Mass is the amount of matter in an object. Weight is the pull of gravity on that mass. Knowing the difference helps you understand science better.

Let’s take a closer look at what is mass and weight and how they are not the same.

What is mass?

"Mass is the amount of matter or "stuff" in an object. It doesn’t change, no matter where the object is."

SI Unit of Mass:

"The SI unit of mass is the kilogram (kg)."

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How to Calculate Mass?

In physics, an object’s mass can be found using different formulas, depending on the available information:

  • Using Density and Volume

3D cube illustration with calculations showing its mass based on density (800 kg/m³) and volume (0.5 m³), resulting in 400 kg.

  • Using Force and Acceleration

Illustration of a box with a formula explaining mass calculation using force and acceleration, showing mass equals 50 kg.

  • Using Weight and Gravitational Acceleration

Illustration of Earth with animals, showing the calculation of mass from weight: 980 N equals 100 kg, using the formula Mass = Weight ÷ g.

What is Weight?

"Weight is the force caused by gravity pulling on an object. It depends on the object's mass and the strength of the gravitational pull in that location."

SI Unit of Weight:

"The SI unit of weight is the newton (N)."

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How to Calculate Weight?

To calculate weight, you can use the formula:

Weight (W) = Mass (m) × Gravitational Acceleration (g)

Illustration explaining the relationship between mass and weight, showing a mass of 20 kg and calculating weight as 196 N.

Differene Between Mass and Weight

Learn the simple differences between mass vs weight!

AspectMassWeight
DefinitionThe amount of matter in an object.The force exerted by gravity on an object’s mass.
UnitKilograms (kg), grams (g), or pounds (lb).Newtons (N), or pounds-force (lbf) in some contexts.
Constant or VariableConstant, remains the same regardless of location.Variable, changes with gravitational acceleration.
Measurement ToolMeasured with a balance, scale, or inertial balance.Measured using a spring scale or force meter.
Depends OnDepends only on the object’s matter, independent of gravity.Depends on the object’s mass and the strength of gravity.
NatureScalar quantity (has magnitude but no direction).Vector quantity (has both magnitude and direction, downward).
DirectionNone, as it is a scalar.Always directed towards the center of the gravitational source.
Value on Earth vs. MoonSame on Earth and Moon.Lower on the Moon (about 1/6th of the weight on Earth).
Effect of GravityNot influenced by changes in gravity.Directly influenced by changes in gravity (stronger gravity means more weight).
Use in PhysicsRepresents inertia, which is the resistance to changes in motion.Represents the force due to gravity acting on a mass.
Role in Newton’s LawsRelated to Newton’s First Law of Motion (inertia).Related to Newton’s Second Law of Motion (F = ma).
Effect in SpaceRemains unchanged in space.Approaches zero in a weightless environment, such as orbit.
Relation to DensityCan be calculated using mass = density × volume.Not related to density; weight is affected by gravitational pull.
Typical ExampleA 10 kg object has a mass of 10 kg whether on Earth, Moon, or in space.A 10 kg object weighs 98 N on Earth but only 16 N on the Moon.
InterchangeabilityCannot be interchanged with weight; they are different concepts.Sometimes mistakenly referred to as “weight” in everyday language.
Common MisconceptionPeople often confuse mass with weight.Often used to describe “heaviness” when it’s actually a force.
Scientific UnderstandingFundamental property of an object that remains constant.A derived quantity based on mass and gravitational force.
Interaction with ForcesDoes not include external forces; purely an intrinsic property.Includes external forces like gravitational pull, which varies by celestial body.
Acceleration EffectsIndependent of acceleration; inertial mass remains constant in all frames of reference.Directly proportional to gravitational acceleration; weight increases as acceleration rises.
Gravitational ConstantMass is the same regardless of variations in gravitational constant.Weight changes if the gravitational constant of a location changes (e.g., on another planet).
Effect in Free Fall Mass remains constant during free fall.Weight becomes negligible during free fall due to apparent weightlessness.
Effect of Air ResistanceUnaffected by air resistance.Apparent weight can change due to opposing forces like air resistance.
Thermal EffectsNot affected by temperature changes.No direct thermal influence; weight only changes with gravity or mass alterations.

How Does Gravity Affect Weight in Different Locations?

Gravity varies across different planets and even across Earth’s surface.

  • On the Moon, gravity is 1/6th of Earth’s gravity, so an object weighs less.
  • In space, astronauts experience weightlessness because there is no gravitational pull.
  • On high mountains, weight decreases slightly due to lower gravitational force.

Why Do Scientists Use Mass Instead of Weight in Physics?

Mass is a constant property, while weight changes with gravity.

  • Scientists use mass for accurate calculations in experiments.
  • Engineers rely on mass to design bridges, vehicles, and aircraft.
  • The kilogram (kg) is the standard SI unit used in the UK and worldwide.

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FAQ’s

Is gram mass or weight?

Gram is a unit of mass, not weight. It measures the amount of matter, independent of gravity’s influence.

How much weight is a mass?

Weight equals mass multiplied by gravitational acceleration. On Earth, weight (N) = mass (kg) × 9.8 m/s² (gravitational acceleration).

Is ton a weight or mass?

Ton is primarily a unit of mass. However, it is sometimes used to express weight in everyday contexts.

How does weightlessness affect astronauts?

UK astronauts, like Tim Peake, experienced weightlessness in space due to the absence of gravity. This causes muscle loss and bone density reduction, requiring astronauts to exercise regularly.

Why does weight change at different points on Earth?

Earth is not a perfect sphere, so gravitational strength varies slightly across locations.
Weight is slightly higher at the poles due to stronger gravity.
Weight is lower at the equator because centrifugal force reduces gravity’s effect.

How does mass affect sports performance?

Rugby players rely on mass for greater impact during tackles.
Sprinters benefit from lower mass for faster acceleration.
Weight categories exist in boxing and weightlifting to ensure fair competition.

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