Physical Quantities

Physical Quantities

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Physical quantities are properties of objects that we can measure using instruments or even our senses. Examples of physical quantities include an object's mass and temperature. We can measure these using instruments, but we can also sense them by simply lifting the object or touching it. So, next time you pick up something or feel its temperature, remember that you're experiencing physical quantities in action! By understanding physical quantities, we can better understand the world around us.

Mass is a physical quantity of an object. Mass per acceleration of gravity gives us the weight of the object
Mass is a physical quantity of an object. Mass per acceleration of gravity gives us the weight of the object

What are the different physical quantities? There is a range of physical properties that we can measure. All these properties are related to an object’s dimensions or its constitution. The seven elemental physical quantities are:

The difference between weight and mass

Weight and mass are two concepts that are often confused. Let's use a ball as an example to explain the difference. The matter that makes up the ball remains the same whether it's on Earth or Mars, but its weight will be different due to the force of gravity. Weight is the amount of force that gravity exerts on an object's mass. This is why a scale measures the gravitational force pulling down on an object's mass. On the other hand, mass is a constant and refers to the amount of matter in an object. So, even though the weight of the ball changes depending on the force of gravity, its mass remains the same. This can be explained with the formula for gravity force. Since gravity is higher on Earth than on Mars, the weight of the ball will be higher on Earth than on Mars, but its mass will always stay the same. Understanding the difference between weight and mass can help us better understand the forces at

What are extensive and intensive quantities?

Physical quantities can be divided into two categories: extensive and intensive quantities. The classification is based on an object's mass. Extensive quantities depend on an object's mass or size, while intensive quantities do not. Mass and electrical charge are examples of extensive physical quantities.

Mass depends on the size of an object. For instance, if you have two steel weights and one is twice the size of the other, the larger one will have twice the mass. This is because the larger object has more matter than the smaller one.

Electrical charge is another example of an extensive physical quantity. If an object's particles have some electrical charge, the number of particles determines the amount of electrical charge the object has. If the object increases its mass, it also increases the number of particles, which in turn increases the electrical charge. Understanding extensive physical quantities can help us better understand the relationship between an object's mass and its properties.

Examples of intensive physical quantities

In contrast to extensive physical quantities, intensive physical quantities do not depend on an object's mass intensive physical quantities include time and temperature.

Time is a fundamental quantity that flows in the same way regardless of the size of objects. For instance, we can measure the time it two objects different mass to from to position B, and time will remain constant in both cases.

Temperature is another example of an intensive physical quantity. If we have an object with a temperature of 100 kelvin and divide it in half, each half will still have the same temperature of 100 kelvin in ideal circumstances where there is no heat transfer. Temperature is a measure of the average kinetic energy of particles in an object, so it does not depend on the object's mass or size.

Understanding the difference between extensive and intensive physical quantities is crucial in physics because it helps us distinguish between properties that depend on an object's mass or size and those that do not.

What are derived physical quantities?

Derived physical quantities properties an object that result from the relationship between two elemental physical quantities. Derived quantities can either result from a relationship between the same physical quantity (e.g., area) or by relating two different ones (e.g., velocity). Below are some examples of derived physical quantities:

Area and volume are derived from length. Area is the amount of space a two-dimensional shape occupies, while volume is the amount of space a three-dimensional object occupies.

Velocity and acceleration are derived from length and time. Velocity is the rate at which an object changes its position with respect to time, while acceleration is the rate at which an object's velocity changes with respect to time.

Density is derived from length and mass. It is the amount of mass per unit volume of an object.

Weight is derived from acceleration and mass. In a planet, acceleration is its gravitational acceleration, and weight is the force exerted on an object due to gravity.

Pressure is derived from force and length. For pressure, the force can be the weight exerted by an object, and the area over which this force acts is related to length.

Understanding derived physical quantities is critical in physics because they help us define and explain the relationship between different physical quantities.

What are some characteristics of physical quantities?

Physical quantities have several characteristics related to their properties. Some of these characteristics are:

  1. No physical quantity can be less than zero, except for electrical charge and temperature values. This means that most physical quantities, such as length, mass, or time, cannot have negative values. However, in some cases, such as temperature, negative values are possible.
  2. Some physical quantities can have a value of zero, such as electrical charge or mass. In these cases, the object is electrically neutral (has no charge) or is massless (light).
  3. Some physical quantities are scalar, which means that they have only a value but no direction. Examples of these quantities are volume, mass, and mole. Scalar quantities can be added, subtracted, multiplied, and divided with other scalar quantities.
  4. Other physical quantities are vectorial, in which case you need the direction to understand what is happening. Examples of vectorial quantities are velocity and acceleration. Vector quantities have both magnitude and direction, and they follow the rules of vector algebra.

Understanding the characteristics of physical quantities is essential in physics because it allows us to properly define and use these quantities in our calculations and experiments.

A thermometer can display a value below zero
A thermometer can display a value below zero

Temperatures below zero are the result of taking the temperature at which water freezes as a zero (0) value. In Celsius, every temperature below the freezing point of water is negative.

How are units and physical quantities linked?

Physical quantities are essential in science as they help us to describe and understand the properties of objects. Units, on the other hand, are the values of reference we use to measure these properties accurately. By comparing an object's physical properties to a standard unit, we can determine its exact value.

There are two types of physical quantities: elemental quantities and derived quantities. Elemental quantities are the seven fundamental properties of an object, such as mass, length, time, temperature, and electrical charge. Derived quantities, on the other hand, are composed of two or more elemental quantities and include quantities such as velocity, density, and pressure.

Physical quantities can also be classified as extensive or intensive. Extensive quantities depend on the size or amount of the substance, while intensive quantities do not. For example, the mass of an object is an extensive quantity, while the density is an intensive quantity.

Understanding physical quantities and units is essential in physics as it allows us to make accurate measurements and calculations. By using standardized units, we can communicate scientific findings and discoveries accurately and precisely.

Physical Quantities

What is a physical quantity?

A physical quantity is a quantity that is used to describe the properties of an object.

What is a vector quantity in physics?

A vector quantity is a physical quantity with a value and a direction. An example of this is velocity. You need the velocity value and its direction to know what is happening.

What are fundamental physical quantities?

A fundamental physical quantity is one of the seven elemental quantities that describe the properties of an object. They are temperature, mass, length, electrical charge, mole, luminosity, and time.

What are the types of physical quantities?

Physical quantities can be extensive or intensive. They are extensive if they depend on the mass or size of the object and intensive if they do not.

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