Difference between velocity and speed

velocity is a vector meaning it has both size and direction so changing direction means changing velocity even if your speed isn't changing

and speed is scalar as it only include size of the speed changing direction dose not mean changing speed. if your traveling in a straight line your sped and velocity are the same at that time .

Basically, velocity has direction. Speed doesn't.

Once you've established which direction is positive and which direction is negative, you can assign a sign to a speed and get a velocity. A train is traveling 50 km/h to the right so it has a velocity of +50 km/h. A train is traveling 50 km/h to the left so it has a velocity of -50 km/h. In both cases, however, the speed of the train is 50 km/h.

You could also apply a bearing angle instead of a sign. Velocity is useful when adding velocities.

In physics, speed is defined as the rate of increase (or decrease) of distance travelled, with time. Linear velocity is the rate of increase (or decrease) of distance traversed by a body in a particular direction. Speed is defined with the omission of reference to direction. Thus, velocity is a vector quantity and speed is a scalar one.

When I was at school, speed was the distance divided by time (miles/hour, for eg). Velocity was speed x mass (or weight). Nowadays, velocity is used to express speed, so a velocity of 10 miles/hour may be used. Weird!

Velocity is a vector and therefore has direction. Speed is a scalar which has no direction so its just a number.

speed is the definate distance traveled over a certain amount of time. velocity is the same just in a specific direction