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Course: Mechanics (Essentials) - Class 11th>Unit 4

Lesson 1: How far do we really go at the end of the day? Exploring the difference between distance and displacement.

Distance and displacement in one dimension

Using a one-dimensional number line to visualize and calculate distance and displacement. Created by Sal Khan.

Want to join the conversation?

• first thank you very much for creating these videos for us. I'm currently in physical science but i've always wanted to learn physics. also i want to ask is all of this going to get any harder than it is right now?
• Oh yeah bud. More complex and more interesting, too.
• How does the lemon move?
• Although this is unnecessary to the actual problem, a lemon can move in many ways, for example, having someone move it. However, it is extremely important to state that a lemon is an arbitrary object, and its being a lemon does not affect the way it moves. Thank you.
• So like in one dimension or on a number line we have 2 directions right(+) or left(-) so if he says 2 to the left it means -2. But in a 3dimension world, we have 4 directions North, South, East, and West.
It was hard to understand!
• Hey azlan,

Think of a dimension in the sense of the Cartesian coordinate system. With it, you can use the same number of values (x, y, z) as dimensions. Each dimension can be represented by another axis, orthogonal (perpendicular) to every other.

With a 1D world, you can define any point on the line with 1 value. In a 2D world, you'll need 2. This is the familiar Cartesian grid system you know and love from math class. You can have positive and negative values on both axes, so you have four directions. In a 3D world, you need 3 coordinate points, and thus you have six "directions": North, East, South, West, up, and down.

Hope this helps,
Hunter
• what is symbol of distance and displacement ?
• Distance is denoted by "d" while most of the books use "x" or "s" for displacement
• What is net displacement? Thanks.
• It is s=vt or displacement equals velocity multiplied by time.
• Displacement Sum of all vectors
Distance Sum of the Absolute value of all vectors
Is this another way to define the difference?
• Distance is the actual path travelled in a given time interval.
Displacement is the difference between the initial and final point of an object at a given time interval.
• Isn't the absolute value of distance travelled always make it positive?
• Yup, that seems pretty right.

Since distance itself is a scalar, with no direction, negative and positive never take place in the value. No left or right.

So it will always be positive.
• Why is it called net displacement?
• It is called net displacement because it is the overall change in position. You would get this by subtracting the initial position from the final position.
• In my textbook , distance is denoted by the letter 's' so is it wrong ?
• no cuz its just a placeholder-some use s, some d, some x...
• What is different distance and displaysment
• Distance is the total amount an object has traveled which is a scalar (only has magnitude but not direction) quantity and it's always a non-negative number and displacement is the change in position of an object and its a vector quantity (has direction and magnitude).