UCSB Science Line
What is displacement?
Question Date: 2017-10-25

An excellent question!

It might be helpful to distinguish between displacement and distance. Both are related, and are different ways to measure lengths.

Distance is a scalar, meaning it is just a number whereas displacement is a vector, meaning it is a number associated with a direction. The distance depends on the path you take, whereas displacement depends only the initial and final coordinates of the moving object.

Let's put this info in a table as a summary.

Distance and Displacement
Distance         Displacement
Type:  Scalar       Vector
Definition:  the total length
of motion
the net length
traveled

Let's say you walk around a 1 m2 table and end up at the same place you started, then....

 Example you will have traveled a distance of 4 meters you will be    displaced 0 meters

Let's say you walk around only three sides of the same table clockwise, then...

 Example you will have traveled a distance of 3 meters you will be   displaced 1 meter   to the left

You could have also taken a really long path around the table, but if you end in the same place you start, your displacement is still 0 m.

Hope this helps!
Best,

Displacement can have a few meanings. When one thing displaces another thing, for instance a dog displacing a cat, it means that the dog pushes the cat away from where the cat originally was, and the dog is now where the cat used to be. When a solid object displaces a liquid, it means that the solid has pushed the liquid out of the way. When the word "displacement" is used in math and physics, it means the shortest distance, in one straight line, between two points. In chemistry, there are displacement reactions, where very small particles replace other very small particles.

Displacement means different things in different contexts. Basically, it means when something takes the place of something else, then the something else is displaced. Displacement of a ship is the amount of water that is moved by the weight of the ship. Displacement in evolution is where a species evolves in a different direction as a result of competition with another species.

The definition of displacement is moving something from its place or position. That means when you move from one side of the room to the other, you've been displaced from your original spot. One important application of displacement happens with fluid. When you get into the bathtub, you'll notice that the water level rises. This is called fluid displacement. Scientists use this to find the volume of objects!

The word "displacement" can mean two things generally: 1. It can mean moving something from its place or position. Technically, if your mom or dad moved you from your bedroom to the bathroom to brush your teeth, they "displaced" you.

2. Displacement can also mean the act of putting something into water, and watching the water level move. This is really cool way of getting to know the exact volume of an object, depending on if the object behaves properly.

If you put smooth rock into a scientific glassware piece known as a "graduated cylinder" that has water in it (it tells you exactly how much volume a liquid is taking up), the water will move the exact volume that the rock takes up. All you have to do is subtract the volume before you added the rock, away from the water with the rock. That will tell you volume of the rock.

You can use this method to figure out how much water something absorbs, which is important for when they're designing something like paper towels or diapers!

Displacement and position are very closely related. When we think of position, we can think of something like a football field. If a runner is on the 20 yard line, his position is 20 yards.

This means when we talk about the runner's position, we really talk about the difference between one point and another special point. For the runner on a football field, we really care about the difference between where the runner is, and a special point we call 0, which is the endzone. If we say we are at position equal to 0, let’s say the runner is still at 20 yards away. This means the difference is just 20 yards.

Displacement is the difference between two points. If we are at the special 0 point, then the runner’s displacement is equal to the difference between his position, 20 yards, and our position, 0. In this way, displacement is more general than position, and when we want to talk about how far something is away, we talk about its displacement from us. I hope this helps!