Velocity can be defined as how fast and in what direction a body is travelling. It is the rate of change of a body’s position relative to a reference frame where the quantity is a function of time. Velocity is strictly connected with the direction of the moving body. Without the factor of direction, the quantity changes to ‘speed’. So it is a vector quantity; direction and magnitude are essential to define it. The scalar value of a velocity is known as speed. It is a derived unit whose value is calculated as metres per second in the SI (metric system). For example, “10 metres per second” is a scalar quantity, whereas “10 metres per second north” is a vector quantity. If there is a variation in direction, speed or both, then the body is said to be experiencing an acceleration. Initial velocity is the body’s velocity at the start of the given time period, whereas the final velocity is the velocity acquired by the body after reaching a certain distance at the end of the given time period. A body possesses constant velocity when it has a constant speed and a constant direction. Constant direction limits the body to move in a straight trajectory. So, constant velocity also means that the body moves in a straight path at a constant speed.
Velocity and Speed
Velocity is the direction and the rate of a body’s movement, while speed is simply the time rate at which a body travels along a path. In other words, velocity is a vector quantity, and speed is a scalar quantity. For example, “80 km/hr south” represents the velocity at which a body is moving, while just “80 km/hr” represents the speed at which the body is moving. The mathematical calculation of velocity is much more complicated than that of speed. The average speed of a body is found by dividing the distance travelled by the time it took for the body to cover the distance. On the other hand, velocity is calculated using many methods, depending on the type of data available about the body. In a typical situation, the average velocity is estimated by dividing the change in position by change in time. The average speed is always greater than or equal to the average velocity. The main reason for this is that the total distance travelled can never be shorter than the displacement, but the displacement can be shorter than that of the total distance travelled.
Equation of Average Velocity
The most common equation of average velocity is:
Where,
A video about average velocity and average speed
Velocity and Acceleration
Velocity is the measure of change of a body’s displacement, while acceleration is the measure of change of velocity. Velocity is a vector value because it is composed of both magnitude and direction. Acceleration is also a vector value as it is just the measure of change of velocity. Velocity can be negative or zero, or positive. Acceleration can be negative or positive, but it cannot be zero, as it is stated as the change in velocity. This explains that there should be some motion for acceleration. The Sl unit of velocity is m/s or ms-¹. The SI unit of acceleration is m/s² or ms-².
Important Velocity Questions with Answers
1) What is meant by velocity?
Answer:
Velocity can be defined as how fast and in what direction a body is travelling. It is the rate of change of a body’s position relative to a reference frame where the quantity is a function of time. Velocity is strictly connected with the direction of the moving body. Without the factor of direction, the quantity changes to ‘speed’. So it is a vector quantity; direction and magnitude are essential to define it. The scalar value of a velocity is known as speed.
2) What is meant by constant velocity?
Answer:
A body possesses constant velocity when it has a constant speed and a constant direction. Constant direction limits the body to move in a straight trajectory. So, constant velocity also means that the body moves in a straight path at a constant speed.
3) Explain the main differences and similarities between velocity and speed.
Answer:
Velocity is the direction and the rate of a body’s movement, while speed is simply the time rate at which a body travels along a path. In other words, velocity is a vector quantity, and speed is a scalar quantity. For example, “80 km/hr south” represents the velocity at which a body is moving, while just “80 km/hr” represents the speed at which the body is moving.
The mathematical calculation of velocity is much more complicated than that of speed. The average speed of a body is found by dividing the distance travelled by the time it took for the body to cover the distance. On the other hand, velocity is calculated using many methods, depending on the type of data available about the body. In a typical situation, the average velocity is estimated by dividing the change in position by change in time.
The average speed is always greater than or equal to the average velocity. The main reason for this is that the total distance travelled can never be shorter than the displacement, but the displacement can be shorter than that of the total distance travelled.
4) Give an example of a vector and scalar quantity.
Answer:
Suppose a bike moves at a speed of 10 m/s. Then, “10 metres per second” is a scalar quantity, whereas “10 metres per second north” is a vector quantity. If there is a variation in direction, speed or both, then the body is said to be experiencing an acceleration.
5) What is the equation of average velocity?
Answer:
The most common equation of average velocity is:
Where,
6) What are the differences between velocity and acceleration?
Answer:
Velocity is the measure of change of a body’s displacement, while acceleration is the measure of change of velocity.
Velocity is a vector value because it is composed of both magnitude and direction. Acceleration is also a vector value as it is just the measure of change of velocity.
Velocity can be negative or zero, or positive. Acceleration can be negative or positive, but it cannot be zero, as it is stated as the change in velocity. This explains that there should be some motion for acceleration.
The Sl unit of velocity is m/s or ms-¹. The SI unit of acceleration is m/s² or ms-².
7) The average ________ is always greater than or equal to the average velocity.
Answer:
Speed
8) Acceleration is a _______ quantity.
Answer:
Vector
9) Speed is a __________ quantity.
Answer:
Scalar
10) __________ is the measure of change of velocity.
Answer:
Acceleration
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Practice Questions
1) What is meant by acceleration?
2) What is meant by speed?
3) What is the relationship between acceleration and velocity?
4) What is a vector quantity?
5) What is a scalar quantity?
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