ICSE Class 7 Answered

What is scalar and I can't understand the difference between velocity ratio and speed

Asked by adhyasharma3735.7sdatl | 20 Apr, 2020, 11:50: AM

Expert Answer

Scalar quantities: - The physical quantities which can specified by its magnitude or its size alone are called scalar quantities.

For example: - distance, speed, mass, time are all scalar quantities. These quantities are specified by their magnitude alone and no direction is required in specifying these quantities.

In other words, the mass of a box is 50 kg. Here 50 kg is the magnitude of quantity - 'mass'

Similarly, distance travelled is 20 metres. Here, 20 m denotes magnitude of quantity - 'distance'

Hope the concept of scalar quantity is clear to you.

Now let's see what is speed.

Speed is the ratio of distance and time.

M a t h e m a t i c a l l y comma space s p e e d space left parenthesis s right parenthesis thin space equals space fraction numerator d i s tan c e space left parenthesis d right parenthesis over denominator t i m e space left parenthesis t right parenthesis end fraction

Speed is a scalar quantity. Because it is specified by its magnitude alone.

For example, if speed of a car is 20 km/h then here, 20 km/h denotes the magnitude of speed.

But,

Velocity is ratio of displacement and time.

M a t h e m a t i c a l l y comma space V e l o c i t y space equals space fraction numerator d i s p l a c e m e n t over denominator t i m e end fraction

Here, velocity (v) is a vector quantity. Also, the displacement is vector quantity.

Let's first understand the meaning of vector quantity.

The physical quantities which are specified by its magnitude as well as direction are called vector quantities.

For example : - velocity, displacement, acceleration, force are all vector quantities.

Let's us understand the these examples in detail.

Whenever we have to specify displacement or any other vector quantity we have to specify it by using direction as well as its magnitude.

For example,

A car moves from point A 20 m North and reaches point B.

Here, we are specifying the displacement of the car by using magnitude which is 20 m and north is the direction of car.

Hope you have understood the difference between vector and scalar quantity as well as velocity and speed.

Remember speed is the ratio of distance and time, while velocity is the ratio of displacement and time.

Speed is scalar quantity and velocity is the vector quantity.

In question, you have mentioned you are not understanding what is velocity ratio.

So remember that, velocity ratio is completely a different concept.

'Velocity ratio' is a term related to machines.

The ratio of velocity of effort to the velocity of load is called velocity ratio of machine.

V e l o c i t y space r a t i o left parenthesis V R right parenthesis space equals space fraction numerator V e l o c i t y space o f space e f f o r t space left parenthesis V subscript E right parenthesis over denominator V e l o c i t y space o f space l o a d space left parenthesis V subscript L right parenthesis end fraction

Answered by Shiwani Sawant | 20 Apr, 2020, 01:46: PM

ICSE Class 7 Answered

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