What is the difference between Speed and Velocity?

Question

Its not Homework but im not really getting it in Class. Can someone explain the whole idea?
Thanks

Answer 1

Velocity V is a vector. It has both speed and direction, and can be represented as an arrow like ------------>. This velocity is going east, which we can call the plus (+) direction; and this one, <------------, is going west, which has to be the minus (-) direction because it is opposite of east.

The length of the arrow represents the magnitude of the velocity, which we call speed. Thus, if ------> is V = 30 mph east, then ------->-------> is 2V = 60 mph east because the arrow is twice as long. If <------- is the velocity, then - V = 30 mph west, because we agreed that west was the minus direction.

Vectors have special rules for adding. To add two vectors, for example, place the tail of one vector onto the point of the other. Thus, from the previous, V + 2V = -------> + -------->-------> = ------->-------->-------> = 3V. We can add any number of vectors just so long as we keep putting tail-to-point in the adding.

They can also be subtracted, which is just a form of negative addition. Thus, V - 2V = V + (-2V) = -------> + <-------<------- = <-------<====> = <------ = - V The, <====> represents the <------- and ------> arrows superimposed on each other. As these two arrows are the same magnitude (speed), but in opposite directions (east vs. west), they cancel out (subtract). This leaves only the one <------ arrow, which is pointing west; so that means minus since east is plus. Therefore, we have the indicated - V.

Here's an easy problem as an example. Suppose you drive 30 mph west, then turn north onto the parkway and drive 40 mph. What would be your resulting overall velocity?

In math talk, that's V = vw + vn; where V is the resulting velocity, vw is the west = 30, and vn = 40 north. These are all vectors, when you sum vectors, you get a vector result.

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|<----- is a (poor) picture of the problem (due to Answers limits). But you can see, we've formed a right triangle with the west velocity as one side and the north velocity as the other. In fact, we've formed a so-called 3,4,5 right triangle; so the V magnitude is v = 50 mph and its direction is the hypoteneuse of the 3,4,5 right triangle.

The direction is the angle theta = arctan(4/3), whatever that is. So the correct V = v theta = 50 mph in the theta direction

Bottom line, speed is the magnitude of a vector. Velocity is what we call that vector when speed is the magnitude.

Answer 2

Speed is a scalar and velocity is a vector.

A scalar quantity, is a physical quantity that has magnitude (size) but has no specifc direction. So when you say speed, you are essentially referring to how fast something is going regardless of the direction in which the speed is occurring. Other examples of scalars are length, time, temperature (notice how these are not associated with any direction)

A vector is similar to a scalar in that it has magnitude, but differs in that it involves a specific direction.
For example, you would say a speed of 5 metres per second, but you would say a velocity of 5 metres per second due east, specifying the direction.
Other examples of vectors are displacment and force

Answer 3

Velocity has a direction. Consider a car travelling on the x-axis at speed 10 m/s

- 10 m/s or 10 m/s

the first one is in the direction of the negative x - axis
the second one is in the direction of the positive x - axis

but the car would have a speed of 10 m/s, regardless of direction

Answer 4

ok.
I think if you are studying the chapter in the class, then you might be familiar with scalar and vector quantities.
Scalar quantities are those units which determine only magnitude of a quantity, whereas vector quantities are those which determine magnitude as well as direction of the thing we are working with.
for ex.- speed is a scalar quantity since it gives only magnitude and velocity is vector quantity as it determines direction also. But when we are solving problems in the starting or the simple problems, we generally ignore the direction. In complex problems only, we consider the direction.

Answer 5

Speed is the distance moved in unit time without considering the direction where as velocity is the rate of change of displacement (displacement = distance moved in a specified direction)

Answer 6

Speed is distance in some time.

Velocity is speed & direction.

Speed: 50 miles per hour
Velocity: 50 miles per hour, north.