What is the difference between velocity and speed? [duplicate]

What is the difference between velocity and speed? could anyone describe it more specific? does velocity have direction?

• yes they are different, velocity have a direction (vector) and speed doesn't (scalar). – PranshuKhandal Mar 4 '19 at 11:39
• it is like that speed of Earth around sun doesn't change but it its velocity does change every time bcoz its direction changes – PranshuKhandal Mar 4 '19 at 11:41
• it is like that speed of Earth around sun doesn't change but it its velocity does change every time bcoz its direction changes – PranshuKhandal Mar 4 '19 at 11:41
• @Fareez M do you know what a vector is? – KV18 Mar 4 '19 at 13:35
• There is already an answer here: physics.stackexchange.com/questions/173109/… – GiorgioP Mar 4 '19 at 14:24

Yes, velocity has direction.

In simple words,

Speed is a scalar quantity and is defined as rate of change of distance wrt time whereas velocity is the rate of change of displacement wrt time. Displacement is in simple words the shortest path between 2 points.

Let us take an example, say a man walks 5 km from Point A to Point B and walks yet again 5 km from Point B to Point A. Here distance covered by man is 10 km but the displacement is 0 since the shortest distance from Point A to Point A is 0. If the man moves from A to B in 5 seconds then the velocity points in the direction of A to B and has a magnitude of 1km/s.

• If a man walk 4 km from point b to point a, is the displacement 1 km? – Fareez M Mar 4 '19 at 11:52
• No, the displacement is 4km. – Vaishakh Sreekanth Menon Mar 4 '19 at 11:54
• Why 4 km? can you explain me why the displacement 4 km? – Fareez M Mar 4 '19 at 11:56
• The man walks 4km from point B to point A right. So displacement is equal to 4km. Displacement is (in simple words) the shortest distance or the distance you get by joining 2 points with a straight line. – Vaishakh Sreekanth Menon Mar 4 '19 at 11:58
• So if the man walk 1 km from point a to point b, the displacement 1 km? – Fareez M Mar 4 '19 at 12:01

Speed is a scalar quantity while velocity is a vector quantity.

I mean to say that whenever you say velocity you associate it with a direction. If you say that your car is moving at $$20$$ $$km$$ $$h^{-1}$$, you give information about its speed but if you also specify the direction your car is moving like $$20$$ $$km$$ $$h^{-1}$$ due north you are telling about you car's velocity. In short we may say that a velocity has two parts to it,

$$1.$$ the speed which expresses the magnitude

$$2.$$ the direction

So you can say that velocity incorporates the idea of direction along with speed.

Using velocity over speed has an advantage to it that you provide complete information about your movement.