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Speed, Velocity and Acceleration

Physics | 7-14 yrs | Interactive

Look around you and observe what you see. You might see people, flowers, birds, cars, buses and many more things. Can you say what is common in everything that you see around? It is motion or movement. Everything in this Universe is moving. The rate of movement of every object around you is different. Some may be moving very fast while others may be moving really slow. But a definite movement is visible in everything around you. You might say that some objects in your room or buildings that you see are not moving, or if you are standing still, you are not moving. But observe that you are living on planet earth which is constantly moving around the sun. The moon is moving around the earth, the sun and planets are moving around the galaxy. Light is moving from one place to another and even a tiny particle of an atom is constantly moving.

Difference between Speed, Velocity and Acceleration?

This movement and the speed of movement have been given some basic terms in Physics. It is known as the Physics of Motion and has terms like Speed, Velocity and Acceleration. Let us take a look at them one by one.

What is Speed?

The terms Speed and Velocity are often used to mean the same thing in everyday life, but both are very different from each other. Speed is the measurement of how fast or slow an object is moving. Speed is a scalar quantity because it can be measured into a numerical value. We know that:

What is the formula for Speed?

Speed= Distance/ Time.

What is Velocity?

Velocity, on the other hand, is the direction in which the object is moving. It is the rate at which the object is changing its position. Velocity is a vector quantity, meaning it consists of two fundamental characteristics. It can be described by both- a numerical value as well as by the direction.

What is the formula for Velocity?

Velocity= (Change in distance) / (change in time)

Let us take an example: A car is going on the highway at the speed of 60 km/hr. Maybe at this particular time the car is being driven at this speed, but it may change its speed later. But here, we do not know the direction at which the car is being driven. But if we say that the car is moving at 60 km/hr in a northern direction, then we know that the Velocity is 60 km/hour north.

What is Acceleration?

Here comes a twist in the story- Acceleration. Acceleration is the measurement of how much the Velocity of an object changes at a certain point of time, which is usually in 1 second. Thus, the Velocity of a moving object can either increase or decrease over time.

So, the car is moving at a speed of 60 km/hour north. The driver pushes down on the gas pedal and the car starts moving faster and faster. This is the change in Velocity and is known as Acceleration.

What is the formula for Acceleration?

Acceleration= (change in velocity) / (change in time)

Let us look at another example. Suppose you are riding a bicycle. You start off by pushing the pedals slowly and after some time you begin to push the pedals really fast. So you are accelerating to increase your speed.

Acceleration is measured in meters/ second squared.

So if you have the Velocity in meters per second and time in seconds, you can calculate the Acceleration by using the formula. Acceleration, like Velocity, is also a vector since it has a numerical magnitude in meters/ second and also has a direction.

When we have an object that changes velocity by a constant amount of time, it is called constant acceleration. Here the object in motion keeps gaining speed or constantly increases its velocity. Suppose you throw a ball onto a slope, it will keep moving downwards, faster and faster every second. On the 1st second the Velocity is 10 m/s, on the 2nd second its Velocity is 15 m/s and on the 3rd second its Velocity is 20 m/s. Thus there is a Constant Acceleration of 5 m/s.

When we have an object that changes its velocity by slowing down or decreasing, it is called Negative acceleration or Deceleration. Suppose you are riding your bicycle and you stop pushing the pedals, the tires will start going slower and slower. This is Negative acceleration. Here the Velocity of a moving object keeps decreasing.

5 Interesting Facts about Speed, Velocity and Acceleration

  1. Gravity is an important cause of acceleration. The Earth’s gravity that pulls a falling object towards it speeds up the acceleration of a falling object. So, if you are diving from a swimming board, you will start at a low speed but speed accelerates each second because of gravity.
  2. Galileo was the first scientist to measure speed.
  3. The fastest possible speed in the entire Universe is that of light. The speed of light is 299,792,458 m/s.
  4. Newton found that the Kinetic energy of a moving object is linear with its mass and the square of its velocity. The mass of an object can change the velocity of the object. The gravities of other planets are different from the Earth’s gravity because they have different masses.
  5. The term ‘Escape Velocity’ is used for the minimum velocity a body must have in order to escape from the gravitational pull of the earth.
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  1. I’ve learned that speed is divided by time and distance. I have also learned that the difference between speed, velocity, and acceleration. The difference between those two are that velocity is the direction in which an object is moving.