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Welcome to our Physics lesson on What is Velocity? How do we measure it?, this is the third lesson of our suite of physics lessons covering the topic of Speed and Velocity in 1 Dimension, you can find links to the other lessons within this tutorial and access additional physics learning resources below this lesson.
As discussed above, Speed is the Distance travelled in the unit of Time. But in the previous tutorials we have learned that there is another quantity besides Speed which is measured in the units of length. This quantity was called Displacement and its shows the change in position of an object. So, what happens is we divide Displacement by Time? Do we still get Speed?
The answer is NO. When dividing Displacement and Time, we obtain a new physical quantity known as Velocity.
Velocity is a vector quantity and it is denoted by v⃗. Its formula is:
(In this instance we are discussing Speed and Velocity in one dimension, so Displacement is written as ∆x⃗ instead of ∆r⃗).
Since Displacement is measured in metres and Time in seconds, the unit of Velocity is [m/s] just like the unit of Speed.
It is obvious Velocity is a vector quantity as it is obtained by dividing a vector by a scalar (look at the Physics tutorial Multiplication of a Vector by a Scalar).
An object moves uniformly for 20 seconds from A to C according the path shown in the figure.
of the object. Take π = 22/7.
The object has moved in such a path that we have a half-circle and a straight line combined. For the half circle, we have:
The Distance s2 is given; it is sBC = s2 = 80m.
Therefore, the total Distance s is:
Displacement (as the shortest path from A to C), represents the hypotenuse of the right triangle formed by the diameter of the half-circle AB and the line BC as shown in the figure.
Thus, since AB = d = 2r = 2 × 35 m = 70 m, we have for the Displacement (The length of the vector AC⃗):
Now, it is easier to calculate the Speed. We simply divide the Distance found at (a) by the Time. Thus,
The same procedure is used to calculate the magnitude of Velocity, i.e. we will divide the Displacement found at (b) by the Time, t. Thus,
You have reach the end of Physics lesson 3.5.3 What is Velocity? How do we measure it?. There are 4 lessons in this physics tutorial covering Speed and Velocity in 1 Dimension, you can access all the lessons from this tutorial below.
|Tutorial ID||Physics Tutorial Title||Tutorial||Video|
|3.5||Speed and Velocity in 1 Dimension|
|Lesson ID||Physics Lesson Title||Lesson||Video|
|3.5.1||What is Speed? How do we measure it?|
|3.5.2||The meaning of Average and Instantaneous Speed|
|3.5.3||What is Velocity? How do we measure it?|
|3.5.4||Average and Instantaneous Velocity|
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