Master the concepts of speed and velocity with clear definitions, formulas, and practical examples.

At Selftution.com – the best educational website for simple, high-quality learning – we break down complex physics topics into easy-to-understand lessons. Welcome to your ultimate learning hub!

So, let’s begin.

For a body in motion, both speed and velocity are measures that help us understand how fast it is moving.

While they may seem similar at first glance, there are key differences between the two.

This post will delve into the concepts of speed and velocity and highlight the differences between them.

Speed is a physical quantity that indicates how fast an object is moving, regardless of the direction.

It represents the rate of motion but does not provide any information about the direction in which the object is traveling.

Velocity, on the other hand, not only measures how fast the object is moving but also specifies the direction of motion.

The fundamental difference lies in the presence of direction.

Speed is a scalar quantity, as it has only magnitude, while velocity is a vector quantity, as it includes both magnitude and direction.

In simpler terms, speed tells us “how fast,” while velocity tells us “how fast and in which direction.“

Skip to the difference between speed and velocity

Difference Between Speed and Velocity – Explained with Examples

SPEED

Definition of Speed –

The speed of a body is the rate of change of distance or the distance traveled by the body in unit time.

It is a scalar quantity. We represent it by the small letter ‘u’ or ‘v’ in italics as ‘u’ or ‘v’. If a body travels a distance ‘S’ in time ‘t’ then the formula for speed ‘v’  is

Speed = Distance / Time

or

v = S / t

S.I. Unit of Speed –

Since the S.I. unit of distance is the meter (m) and time is second (s), thus, the S.I. unit of speed is the meter per second or m/s (ms^-1).

VELOCITY

Definition of Velocity –

The velocity of a body is the displacement of the body in unit time or the distance traveled by it in a unit time in a particular direction or the rate of change of displacement of a body.

It is a vector quantity. We represent it by the small letter ‘u’ or ‘v’ in bold as ‘u’ or ‘v’. If the displacement of a body is ‘S’ in time ‘t’, then the formula for velocity ‘v’  is

Velocity = Displacement / Time

or

v = S / t

Note: For velocity, both magnitude and direction need to be specified. The two bodies move with the same velocity when they move at the same speed and in the same direction. However, velocities are different if both are moving at the same speed in an opposite or any other direction.

S.I. Unit of Velocity –

As the S.I. unit of both distance and displacement is the same, i.e., meter (m). Therefore, the S.I. unit of both velocity and speed is a meter per second or m/s (ms^-1).

UNIFORM SPEED AND VELOCITY

Uniform Speed

A body is said to be moving with a uniform speed when there is no change in speed with time.

Or

A body is said to be moving with a uniform speed when the rate of change of distance is the same throughout its motion.

Or

A body is said to be moving with a uniform speed if it covers equal distances in equal intervals of time.

Examples of uniform Speed:

1. A car cruising on a highway with its speed locked on,
2. A ball rolling on a frictionless horizontal surface, etc.

Uniform Velocity

A body is said to be moving with a uniform velocity when there is no change in velocity with time.

Or

A body is said to be moving with a uniform velocity when the rate of change of displacement is uniform throughout its motion.

Or

A body is said to be moving with a uniform velocity if it travels equal distances in a particular direction, in equal intervals of time.

Examples of uniform velocity:

1. A car cruising on the highway towards the north with its speed locked on,
2. A ball rolling on a frictionless horizontal surface in any particular direction, etc.

NON-UNIFORM SPEED AND VELOCITY

Non-uniform Speed

A body is said to be moving with a non-uniform speed when the speed of the body changes with time.

Or

A body is said to be moving with a non-uniform speed when the rate of change of distance varies throughout its motion.

Or

A body is said to be moving with a non-uniform speed if it covers unequal distances in equal intervals of time.

Examples of non-uniform speed:

1. A car cruising on a busy market street,
2. A ball rolling on a rough surface, etc.

Non-uniform or Variable Velocity

A body is said to be moving with a non-uniform velocity when the velocity of the body changes with time.

Or

A body is said to be moving with a non-uniform velocity when the rate of change of displacement varies throughout its motion.

Or

A body is said to be moving with a non-uniform velocity if it travels unequal distances in a particular direction, in equal intervals of time.

Or

A body is said to be moving with a non-uniform velocity if it travels equal distances in different directions, in equal intervals of time.

Examples of non-uniform or variable velocity:

1. The motion of a freely falling body is an example of non-uniform velocity, as direction does not change, but speed increases continuously.
2. Similarly, the motion of a body in a circular path, even with uniform speed, is an example of non-uniform velocity as the direction of the moving body changes continuously.

When a body moves with non-uniform or variable speed, then we specify the instantaneous speed and the average speed. Likewise, when a body moves with non-uniform or variable velocity, then we specify the instantaneous velocity and the average velocity.

INSTANTANEOUS SPEED AND VELOCITY

Instantaneous Speed

For a body in non-uniform motion, its speed at any instant is called the instantaneous speed. It is the ratio of the distance traveled in a very short interval of time to the time interval. Thus, the formula for instantaneous speed is –

Instantaneous speed = Distance traveled in a short interval of time / Time interval

A speedometer or speed meter is an instrument that measures and displays the instantaneous speed of a vehicle.

Instantaneous Velocity

For a body moving with variable velocity, the velocity at any instant is called its instantaneous velocity. It is the ratio of the displacement of a body in a very short interval of time to the time interval. Thus, the formula for instantaneous velocity  is –

Instantaneous velocity = Displacement of a body in a short interval of time / Time interval

To measure instantaneous velocity, the time interval shall be small enough so that the direction of the motion of a body does not change during this interval.

AVERAGE SPEED AND VELOCITY

Average Speed

The ratio of the total distance traveled by a body to the total time taken for the journey is average speed. Thus, the formula for average speed is –

Average speed = Total distance traveled / Total time taken

For a body in uniform motion, the average speed and the instantaneous speed are equal.

Average Velocity

It is the ratio of the displacement of a body to the total time taken for the same. Thus, the average velocity is –

Average velocity = Displacement / Total time taken

DIFFERENCE BETWEEN SPEED AND VELOCITY

1. The speed is a scalar quantity, while velocity is a vector quantity. The speed and velocity of a body at a given interval of time tell us how fast the body is moving at that time. Velocity provides us with additional information and tells us the direction in which the body is moving.
2. For the motion in a straight line magnitude of speed and velocity is the same. However, the speed is always positive, but velocity can be negative or positive depending on its direction of motion.
3. The average velocity of a body can be zero, even when its average speed is not zero.

Difference between speed and velocity in tabular form:

Difference between speed and velocity

For more such information, please visit our YouTube channel SELFTUTION

The post Difference Between Speed And Velocity With Examples appeared first on Selftution.

Your go-to resource for simple, effective learning. Welcome to Selftution.com – where complex concepts become easy!

Children often use distance and displacement interchangeably, but only a few understand the difference between them.

Yes, you read that right, they are not the same.

Distance and displacement are two physical quantities related to the measurement of length.

Distance is the total length of the path traveled by an object, whereas displacement is the shortest straight-line distance between the initial and final positions of the object.

Let’s delve deeper into the concepts of distance and displacement and explore the differences between them.

DISTANCE

Definition of distance – 

Distance is the total length of a path through which a body moves. The distance traveled by a body depends on the path followed by the body.

Distance is a scalar quantity; thus, it does not depend on the direction in which a body moves. We represent the distance by the letter ‘S‘. The SI unit of distance is meter (m). Therefore, we need the following two parameters to express distance completely – unit in meters (m) and the numerical value of its magnitude.

Back to the top

DISPLACEMENT

Definition of displacement – 

Displacement is the shortest distance from the initial to the final position of the body. The length between the two points is the magnitude of displacement and its direction is from the initial position to the final position.

Displacement is a vector quantity; thus, it depends on the direction in which a body moves. We represent displacement with the bold letter ‘S‘. The SI unit of distance is also the meter (m).

Difference Between Distance and Displacement

Representation of Displacement –

The displacement is a vector represented by a straight line with an arrow.  The tip of the arrow on the straight line represents the direction of displacement, while the length of the straight line on a proper scale represents its magnitude. Therefore, we need the following three parameters to express displacement completely: unit in meters, the numerical value of its magnitude, and the direction in which a body moves.

Back to the top

THREE IMPORTANT DIFFERENCES BETWEEN DISTANCE AND DISPLACEMENT

The magnitude of displacement is either equal to or less than the distance

If a motion is in a straight line along a fixed direction, the magnitude of distance and displacement is equal to that of distance. Whereas, if motion is along a curve or any zig-zag path, the magnitude of displacement is always less than that of the distance. The magnitude of displacement can never be greater than the distance traveled by the body.

The distance is always positive, whereas displacement can be both negative as well positive

The distance is the length of the path traveled by a body, so it is always positive. On the other hand, displacement is the shortest length in the direction from the initial to the final position. So, it can be positive as well as negative depending on its direction.

The displacement can be zero even if the distance is not zero

If a body, after traveling, comes back to its starting point, then its displacement is zero, but its distance is not zero. For example, the motion of a stone thrown vertically upward and the circular motion of a body. In both cases, the body returns to its initial position after traveling a certain distance.

Difference between distance and displacement

Back to the top

For more such information, please visit our YouTube channel SELFTUTION

The post Difference Between Distance and Displacement appeared first on Selftution.

Master the concepts of work and energy in physics with clear definitions, practical formulas, and real-world applications.

At Selftution.com, we simplify complex science topics – making us the best educational website for students and lifelong learners!

In physics, the terms work and energy have specific meanings that differ from how we commonly use them in our day-to-day lives.

Daily activities like playing, pedaling a bicycle, or carrying a load are examples of physical work. Reading, solving problems, or thinking are considered mental work.

Both physical and mental tasks consume energy. However, physics only recognizes physical work, and only when there is a displacement or a change in an object’s shape or size.

For instance, in physics, solving homework while sitting in one place is not considered work. Mental effort doesn’t meet the physical criteria of displacement.

Understanding the unique definitions of work and energy in physics reveals their true nature. Let’s explore their definitions and examples in detail.

WORK DONE IN PHYSICS

A force tends to move or stop an object upon which it acts. If the object moves in the direction of the force or there is a change in speed or direction of motion, we say work is done. Sometimes, work is said to be done even when there is no displacement; rather, there is a change in the shape or size of the body.

Definition of Work-

If on applying force on an object, the motion or direction of object changes or shape or size of the objects changes, the work is said to be done by the force.

Examples of WORK DONE are-

Examples of work done in physics due to a change in position or displacement, or a change in speed or direction, or  a change in shape or size are :

Different examples of work done in physics due to a change in position or displacement or a change in speed or direction, a change in shape, or size

Examples of WORK NOT DONE are-

• If two teams of tug-of-war apply an equal pulling force, no work is done because there is no change in the position of both teams.
• If you push a wall, you waste a lot of energy, but as per physics, the work done is zero because there is no displacement.
• When a porter is standing still on a railway platform with heavy luggage on his head, he is not doing any work.

 FACTORS AFFECTING WORK

From the above examples, we conclude that the work done depends on the following two factors:

1. The magnitude of the force applied to the object, and
2. The displacement and not the distance moved by the object in the direction of the force.

We can now define work as the product of force and displacement.

Work = Force x Displacement

W = F x S

Therefore, the new definition of work is as follows:

The work done by a force on a body is equal to the product of the force applied and the displacement of the body in the direction of the force.

Unit of Work

James Prescot Joules

Since the unit of force is the newton (N) and that of displacement is the meter (m), therefore, the unit of work is the newton-meter (Nm). We also call the Newton-meter Joule (J), named after J. P. Joule, a scientist who did several experiments in the field of energy. James Prescot Joule (1818-1889) was a British Physicist. He was famous for his extensive work on heat and the conversion of heat into work. He verified the law of conservation of energy. A joule is the SI unit of both work and energy.

RELATION BETWEEN WORK AND ENERGY IN PHYSICS

Work and energy are very common terms used in our day-to-day life. After doing whole day activities, we feel a loss of energy and we are unable to do any more work. So, we say that we do not have any more energy left in our bodies to do any more work. Thus, energy and the ability to do work are related to each other. Without using the energy, we cannot perform any work.

Definition of energy –

Energy is the ability or capacity to do work.

Hence, we say that there is a direct relationship between work and energy in physics. Energy is the cause, and work is its effect. Therefore, the unit of energy is also Joule (J), which is the same as that of work.

When work is done on a body, its energy increases. In other words, the work done on the body is stored in the form of energy. But if work is done by the body, its energy decreases. In other words, energy is spent when a body does work. For example, a boy, while playing football, runs all over the field and spends energy doing work. He will continue to play football till he possesses energy.

As per the law of conservation of energy, energy can neither be created nor destroyed. However, while doing work, one form of energy changes from one form to another. To know about different forms of energy, refer to my earlier post – Different forms of energy in Physics with examples.

You may also like…... Types of Chemical Reactions in Chemistry

The post Work and Energy in Physics | Definition & Examples appeared first on Selftution.

Master the fundamentals with Selftution.com – the best educational website for clear, simplified learning. Understand scalar and vector quantities with real-world examples, interactive diagrams, and practice problems.

Welcome to a smarter way to learn! So, let’s begin.

In physics, a physical quantity is anything that can be measured, and it falls into one of two categories: scalar and vector quantities.

Scalars are defined solely by their magnitude, while vectors require both magnitude and direction for a complete description.

The key difference between scalar and vector quantities lies in the presence of direction.

While scalar quantities like distance or temperature can be fully described by a numerical value, vector quantities like velocity or force also need direction to convey their full meaning.

This post will dive deeper into scalar and vector quantities, exploring examples and highlighting their differences.

If you’re looking to learn more about physical quantities and measurements, check out our guide on the Basics of Measurement for Kids.

SCALAR QUANTITY

Definition of a scalar quantity –

Scalar quantities are those physical quantities which are expressed only by their magnitude along with the unit required for the measurement.

For example, if we state that the mass of a bag is 5.0 kg, this information is complete by itself. It conveys both the amount (mass) and the unit of measurement (kilograms), without requiring any additional details such as direction. In this case, the mass is fully expressed as a scalar quantity because we don’t need to know where the bag is or in which direction it’s moving; the value and the unit are sufficient.

To completely define a scalar quantity, we need two essential components:

1. The numerical value of the measured quantity indicates “how much” of the quantity we are dealing with.
2. The unit in which the quantity is being measured tells us the standard of measurement, such as kilograms, meters, or seconds.

Together, these provide the magnitude of the scalar quantity. Importantly, the magnitude is always positive, as it represents the size or amount of the quantity without the need for direction.

Examples of scalar quantities

Some of the examples of scalar quantities are – mass, time, length/distance, density, volume, temperature, speed, pressure, energy, power, charge, resistance, mechanical advantage, electric and magnetic potential, angle, etc.

We represent a scalar quantity symbolically by its English letter. For example, ‘m’ denotes mass, ‘t’ time, ‘d’ distance, ‘s’ speed, etc. Scalar quantities can be added, subtracted, multiplied, and divided by simple mathematical methods.

Difference between scalar and vector quantities with examples

VECTOR QUANTITY

Definition of a vector quantity –

Vector quantities are those physical quantities which require both magnitude and direction to represent them along with the unit required for the measurement.

For example, if we say “Displace a stone by 10 meters,” the first question that naturally arises is, “In which direction?” Without specifying the direction, the statement is incomplete. Displacement is not fully described by magnitude alone. However, if we say “Displace the stone by 10 meters towards the north,” the instruction becomes clear and meaningful.

To fully express a vector quantity, we require the following three components:

1. The numerical value of the measured quantity indicates the magnitude.
2. The unit in which the quantity is measured, such as meters, newtons, etc.
3. The direction of the quantity specifies where or in what direction the measurement is applied.

These three elements together—magnitude, unit, and direction—are essential to completely describe a vector quantity. Without any one of them, the description remains incomplete.

The numerical value of a vector quantity, along with its unit, gives us the magnitude of the quantity. The negative sign with a vector quantity implies a reverse or opposite direction. Thus, vector quantities can be positive as well as negative.

Examples of vector quantities

Some of the examples of vector quantities are – displacement, velocity, force, acceleration, electric field, magnetic field, weight, torque, temperature gradient, etc.

A vector quantity is generally written symbolically by its English letter bearing an arrow on it. Sometimes vector quantity is also represented by a bold English letter. For example, ‘d‘ denotes displacement, ‘v‘ velocity, ‘a‘ acceleration, ‘F‘ force, etc. Kindly note that ‘F‘ and ‘- F‘ are two equal forces acting in opposite directions. We cannot perform simple mathematical operations on vector quantities, unlike scalar quantities. Vector quantities follow different algebra for their addition, subtraction, and multiplication.

DIFFERENCE BETWEEN SCALAR AND VECTOR QUANTITIES

• Scalar quantities are those physical quantities that are expressed only by their magnitude, whereas vector quantities require both magnitude and direction to completely express them.
• The scalar quantities are always positive, whereas vector quantities can be positive as well as negative.
• A simple mathematical operation can be performed on scalar quantities, whereas vector quantities follow complex algebra for their addition, subtraction, and multiplication.

Difference between scalar and vector quantities in tabular form:

Let us understand the difference between these two quantities in terms of distance and displacement.

Difference between scalar and vector quantities

For more such information, please visit are YouTube channel SELFTUTION

The post Scalar and Vector Quantities |Differences & Examples appeared first on Selftution.