Showing posts with label physics. Show all posts
Showing posts with label physics. Show all posts
What Is The Difference Between Speed And Velocity And Acceleration?

What Is The Difference Between Speed And Velocity And Acceleration?



Speed, velocity and acceleration describe the motion of a body but there is a difference between speed, velocity and acceleration. The rate at which a body move is known as its speed. We can define speed as distance travelled by a body in unit time is known as its speed. On the other hand, the velocity of a body tells us how fast a body is moving in a particular direction. We can define velocity as the time rate of change of displacement of a body is known as velocity. If we talk about acceleration, we come to know that the time rate of change of velocity is known as acceleration. Here, we will briefly explain speed, velocity and acceleration. After reading this article, you will clearly understand the difference between speed, velocity and acceleration.

What is speed?

As we have discussed earlier that distance travelled by a body in unit time is known as its speed. It is a scalar quantity because it is completely described by its magnitude and we don’t require direction to describe it. If the speed of an object is higher, it means that it moving at a faster rate. If the speed of an object is lower, it means that it is moving at a slower speed. As an SI unit of distance is ‘m’ and SI unit of time is ‘s’, therefore, the SI unit of speed is ‘m/s’.

Formula to calculate the speed

We can easily calculate the speed of an object by using the following formula;
       r= d/t
Here, r is known as speed, d is known as distance travelled and t is known as the time taken to travel this distance.

Numerical relevant to speed

A cyclist covers a distance of 200 meters in 20 seconds, find out its speed.
Solution:
Distance travelled by the cyclist = 200 meters
Time taken to travel this distance = 20 seconds
Speed = Distance / Time
Speed = 200/20
Speed = 10 m/s

What is velocity?

The time rate of change of displacement is known as velocity. The velocity of a body tells us how fast a body is moving in a particular direction. Therefore, velocity is a vector quantity because there requires magnitude as well as direction for its complete description. SI unit of velocity is m/s.

Uniform velocity

If a body covers equal displacement in equal intervals of time, its velocity is known as uniform velocity. Graph of uniform velocity gives us a straight line.

Variable velocity

If a body covers unequal displacement in equal intervals of time, its velocity is known as variable velocity. Graph of variable velocity doesn’t give us a straight line.

Formula to calculate the velocity

We can calculate the velocity of an object by using the following formula;
Velocity = Displacement / Time

Numerical relevant to velocity

If a man walks 300 m East in 100 seconds, find out its velocity?
Solution:
Displacement = 300m  ,    Time  = 100 seconds
Velocity = Displacement / Time
Velocity = 300/100
Velocity = 3 m/s

Difference between speed and velocity

After getting an idea about speed and velocity, we are able to compare these two quantities. The main difference between speed and velocity is explained below;
    1)    The first difference between speed and velocity is in their meanings. The meaning of speed is the distance covered by a body in unit time, whereas, the meaning of velocity is the displacement covered by a body in unit time.
    2)    Speed of a body tells us how fast a body is moving. On the other hand, the velocity of a body tells us how fast and in which direction a body is moving.
    3)    Speed is a scalar quantity because we don’t require direction for its complete description. Velocity is a vector quantity because there requires magnitude as well as direction for its complete description.
    4)    Speed of an object is always positive. On the other hand, the velocity of an object can be positive as well as negative.

What is the acceleration?

The time rate of change of velocity is known as acceleration. Acceleration is a vector quantity because there requires magnitude as well as direction for its complete description. If the velocity of a body is increasing, its acceleration is positive. On the other hand, if the velocity of a body is decreasing, its acceleration is negative. Unit of acceleration is meter per Second Square. Formula to find out the acceleration of an object is given below;
Acceleration = Velocity / Time

Uniform acceleration

If the velocity of an object is the same in equal intervals of time, its acceleration is known as uniform acceleration. If we draw a graph between velocity and time, we get a straight line.

Variable acceleration

If the velocity of an object is changing in equal intervals of time, its acceleration is known as variable acceleration. If we draw a graph between velocity and time, we can’t get a straight line.

Numerical relevant to acceleration


If a car starts from zero and gains a velocity of 36km/h after 20 seconds, find out its acceleration.
Solution:
As we know that km/h is not the SI unit of velocity, therefore, before solving it, we have to convert it into an SI unit that is m/s.
Velocity = 36km/h = 10 m/s
Time = 20 seconds
Acceleration = Change in velocity / time
Acceleration = 10 – 0 / 20
Acceleration = 0.5 meter per second square

Difference between velocity and acceleration


While studying motion, we have to come across with velocity and acceleration. Most of the students are not able to understand the difference between velocity and acceleration. The key difference between velocity and acceleration is given below;
     1)    There is a difference between the meanings of velocity and acceleration. The velocity of an object is implied on the speed of an object. On the other hand, acceleration of an object is implied on the change in the velocity.  
     2)    There is also a difference between the definitions of velocity and acceleration. We define velocity as the rate of change in displacement. On the other hand, the acceleration of an object is defined as the time rate of change in velocity.
    3)    The velocity of an object tells us the speed and moving direction of an object. On the other hand, the acceleration of an object tells us how the velocity of an object is changing.
    4)    We can find the velocity of an object by dividing displacement over time. On the other hand, we can find acceleration by dividing velocity over time.
    5)    Unit of velocity is meter per second and unit of acceleration is meter per Second Square.




Why the colour of sky is blue?

Why the colour of sky is blue?



As we know that there are different colours in the world like blue, white, red, yellow and so on but when we see at the sky, a question comes to our mind that why the colour of the sky is blue instead of white, red, yellow or any other colour. It is a complicated concept and before understanding this concept, we have to understand some other things.

Sunlight

The blue colour of the sky is due to the sunlight. We see that the colour of sunlight is yellow but it is not the actual colour of sunlight. The actual colour of sunlight is white and white light is a combination of seven colours. The seven colours of white light are given below;
      Violet
         Blue
       Indigo
      Green
      Yellow
      Orange
      Red

Wavelengths of different colours of light

The wavelengths of these seven colours of light are also different from each other. The wavelength of violet colour is 380-450 nanometers. The wavelength of blue colour is 450-485 nanometers. The wavelength of indigo colour is 485-500 nanometers. The wavelength of green colour is 500-565 nanometers. The wavelength of yellow colour is 565-590 nanometers. The wavelength of orange colour is 590-625 nanometers. The wavelength of red colour is from 625-740 nanometers.

Scattering phenomenon

The blue colour of the sky is due to the scattering of the sunlight. According to the Rayleigh scattering formula, the light which has smaller wavelength scatters more and the light which has a larger wavelength scatter less. In the above seven colours of sunlight, the violet colour scatters more. After that, the blue colour scatters and so on.

The visible wavelength of the light

The portion of the electromagnetic spectrum that is visible to a human eye is known as the visible spectrum. The electromagnetic radiation in this range of the wavelengths is known as the visible light. A human eye can see only that light whose range is in between 400-740 nanometers.

Why the colour of the sky is blue?

When the sunlight which is a combination of seven colours (Violet, blue, indigo, green, yellow, orange and red) enters into the atmosphere of our earth, it is scattered by the gasses and other particles that are present in the atmosphere of the earth. According to the scattering phenomenon, the violet light scatters more but the scattering wavelength of this light is less than 400 nanometers which are invisible for a human eye. After that blue light scatters and the wavelength of blue light is from 450-485 nanometers and this wavelength of the light is easily visible for a human eye. After that other colours of light are scattered. Due to the scattering dominance of the blue light over the other colours of light, the colour of the sky seems blue to us.

Why the colour of the sun is yellow?

As we have discussed earlier that actual colour of the sun is white instead of yellow. According to the scattering phenomenon, violet, blue, indigo and green colours of light have smaller wavelengths, therefore, these colours of light are easily scattered. On the other hand, other colours of light like yellow, orange and red are not easily scattered. That’s why the colour of the sun is yellow.

Is the sky blue because of the ocean?

Most of the people think that the blue colour of the sky is due to the blue colour of the ocean. It is totally a misconception because the blue colour of the sky is due to the scattering of the sunlight. Now, another question comes to our mind that why the colour of the ocean is blue? NOAA (National Oceanic Atmospheric Administration) has provided the answer to this question. According to NOAA, the water can easily absorb the shorter and longer wavelengths of light. Therefore, when sunlight hits the ocean, it absorbs its longer wavelengths like red, yellow, green and orange along with its shorter wavelength like violet. Therefore, there remains only a blue wavelength of light. This blue wavelength of the light is reflected by the ocean. That’s why the colour of the ocean is blue.

Why is the Mars sky red?

The Viking Mars Landers has sent some photos of Mars sky. It is clearly seen in these pictures that the colour of Mars sky is red instead of blue. According to scientists, the red colour of the Mars sky is due to the dust storms which occur from time to time on Mars. These dust storms throw iron-rich dust particles into the atmosphere of Mars. These iron-rich dust particles are the main cause of the red colour of Mars sky. The scientists have also predicted that the colour of the Mars sky also changes with the changes in the weather conditions. If there are no storms for lots of time, the colour of the sky will be blue.

Why are clouds white?

As we know that there are some particles of water in the atmosphere of water. These particles of water are bigger than other particles of the atmosphere. When the white light of the sun strikes with these water particles, these water particles scatter all the wavelengths of light in equal amount. This combination of all the wavelengths of light provides white colour to the clouds.

Why are rain clouds dark?

It is a fact that most of the clouds are white but the rain clouds are a darker shade of grey. The water on our earth changes into water vapours due to warmer earth and these water vapours are less in weight and they rise up. When these water vapours enter into the higher atmosphere of earth, they have to come across with cooler air. The cooler air condenses these water vapours. As a result, they form clouds. No doubt, these water droplets reflect all the colours of sunlight and these are white in colour but when lots of water droplets are gathered, they become thicker and denser. The upper side of these thicker and denser clouds reflects all the colours of light and they don’t allow the light to penetrate through. That’s why the lower side of the rain clouds has a darker shade of grey.






What is the difference between mass and weight?





Mass and weight are two commonly used terms in Physics. In the beginning, most of the students think that mass and weight are synonyms of each other. It is not a fact because mass and weight are two different terms because mass is known as the property of a body and weight is force acting on a body. In order to clearly understand the difference between mass and weight, we have to take an overview of different parameters.

Difference between mass and weight

Mass and weight are different from each other on the basis of different parameters. Here, we compare these parameters one by one.

Difference between definitions of mass and weight





Mass is known as the property of the matter and with the help of mass, we can easily measure the strength of the gravitational attraction of a body. On the other hand, weight is the amount of force that is acting on the body. This force can acts on a body either due to gravity or any kind of the reaction force.
Difference between their quantities


As we know that there are two types of physical quantities. First is the scalar quantity and the second is a vector quantity. There is also a clear difference between vector and scalar quantities. Mass of an object is a scalar quantity. Its reason is that to measure the mass of an object, we just need magnitude and unit. On the other hand, the weight of an object is a vector quantity because if we want to measure the weight of an object, we need its magnitude, unit and direction.
Difference between values of mass and weight
We can also observe a clear difference between the values of these two terms. The value of mass is the same at all the places because it doesn’t depend upon gravity. Therefore, we can say that the mass of an object can never be zero.
Conversely, weight of an object depends upon gravity. Therefore, it has different values in different places. For example, the weight of an object has two different values at Earth and Moon due to the difference in the values of gravity at Earth and Moon. On the other hand, the mass of an object remains the same on the Earth as well as on the Moon.
Different values at different locations
If we change the location of an object, we can’t see any kind of difference in the mass of an object. On the other hand, if we change the location of an object, we can see a definite difference in the weight of an object. If we going higher and higher, the value of gravity will decrease. As a result, the weight of an object also decreases. Conversely, if we are decreasing our altitude, the value of gravity will increase and we see a definite increase in the value of the weight of an object.
The difference between measuring instruments of mass and weight
It is a fact that if we are going to measure anything, we require a measuring instrument. In a similar way, either we are going to measure the mass of an object or weight of an object, we require measuring instruments. As mass and weight are two different terms, therefore, there require two different measuring instruments to measure these two terms. We can easily measure the mass of an object with the help of an ordinary balance. On the other hand, to measure the weight of an object, there requires spring balance.
Difference between their units
A standard for the measurement of an object is known as a unit. To measure the mass and weight of an object, we have to use two different units. The SI (System International) unit to measure the mass of an object is Kilogram and it is abbreviated as Kg. On the other hand, the SI (System International) unit to measure the weight of an object is Newton and it is abbreviated as N.
Difference between their formulas
In Physics, we can’t deny the importance of Mathematics because there require mathematical formulas to measure different terms. The formula to measure the mass of an object is given below;
F = ma                or             m = F/a
We can easily measure the mass of an object if we know the values of force and acceleration of this object. The formula to measure the weight of an object is also given below;
W = mg
We can easily measure the weight of an object if we know the values of mass and gravity of this object.
With the help of these formulas, it is also possible for us to convert the mass of an object into weight and vice versa. For example, if the mass of an object is 10Kg, we can convert it into weight in the following way;
W = 10*9.8 = 90.8N
External factors affecting mass and weight
As we know that mass is an intrinsic property of an object and that’s why there is no external factor that can affect the mass of an object. On the other hand, the weight of an object depends upon the mass of that object. Therefore, the force of attraction can easily influence the value of the weight of that object. That’s why if you are going to measure the quantity of an object, it is better for you to use mass rather than weight. Its reason is that the mass of an object remains the same at all the places, whereas, the weight of an object changes by changing the altitude.
Why we use mass in the formula to measure weight?
Most of the students think that due to lots of differences between mass and weight, why we are still using mass in the formula to measure weight. Its answer is that the weight of an object is due to the gravitational force that attracts a body. If the mass of an object is very small, the value of the gravitational force will also be small. That’s why we can observe that a fog particle remain suspended in the air. Due to this reason, it is necessary for us to use mass in the formula of the weight. Another reason is that mass is the functional property of the matter and weight is known as the consequence of that property.
To sum up, we can say that mass and weight depends on each other. Greater the value of the mass, greater will be its weight and vice versa. The main difference between two terms is that mass is a constant quantity, whereas, the weight of an object changes with the change in the altitude.
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