Speed and Velocity

Physics homework for 10/08/14: 

“Speed and Velocity” Blog Post - Write your own definition of speed and velocity, highlighting the difference between the two. Describe an example of both average velocity and instantaneous velocity in your own life (not one covered in class)

Wednesday, October 8th, 2014

                         Speed and Velocity 

       Today in class we mainly took notes, did some velocity problems, wrote some definition down, and we also discussed and reviewed everything together. We mainly learned about equations and velocity today, we also talked about variables and what not. And we illustrated some key points about some things like equations.

       

Moving onto some definitions though, speed is the rate of distance covered in a given amount of time and velocity is speed with a direction - but these are the notebook definitions! In my own words, I would define speed as how fast you are traveling in a certain length of time. Or maybe I would describe it as the rate you are traveling by depending on your distance and your time or as the rate at which an object covers a certain distance/how fast something is moving. As for velocity, I would basically call it the rate at which something is traveling by depending on distance and time, but with a direction, whether the direction is a loop-de-loop or just a simple north or even a southwest or something velocity has direction. 

Now, because velocity has direction and magnitude (size) it is a vector quantity. Since speed has only magnitude it is a scalar quantity. We have not talked much about these things yet, but we will probably delve into them soon.

Velocity and speed are quite similar, but also quite different in many ways, here are a few ways in which they are similar:

*Speed and velocity both use t and a delta.

*They both usually require you to find the difference between something final and something initial.

*Both equations require division.

*The units for both are m/s. 

*Both have speed or a rate at which they are going.

While both speed and velocity have similarities (many more than I have listed), they also have differences.

Here is a list of some of the differences:
~Velocity has direction unlike speed, therefore it is a vector quantity. And speed is a scalar quantity.

~There are a few types of velocity (instantaneous and average) and apparently not many types of speed. But basically both of them have different sub-divisions.

~With speed "d" (distance) is used in the equation to find speed and "s" is used as well. Whereas with velocity "v" (velocity) is used and "delta x" (change in "x"). And notice an "x" is used; not a "d", even though "delta d" would most likely be the same thing as "delta x." 

~In velocity you have to find the displacement of whatever is moving, on the other hand with speed you are given a distance and just need to plug it into the equation.

Those are the main differences I can think of, but there might be a few more.

Real Life Examples of Velocity

Moving on to the types of velocity we have learned about. Along with the notes and what not we also learned about instantaneous and average velocity. Average velocity is the velocity over a given period of time. Basically it is your velocity when averaged. 

So let's say a truck is zooming by, the truck has velocity but it is not the same the whole way through. Since it is not the same the whole way through you would try and find the average velocity of the truck by taking a few different individual velocities on the truck's journey and averaging them. Or even just two velocities. You would probably do this by combining (or maybe subtracting velocities) and then dividing by the number of information.

Instantaneous velocity is easier to figure out, instantaneous velocity is the velocity at any given moment in time or at any instant. Let's go back to that truck, let's say some time in on the truck's journey the truck's velocity is something like this: "# m/3 (direction)" - in that instant, that would be the truck's instantaneous velocity. At this very moment, some cars on the road might have instantaneous velocities that are above the limit. And also at this moment a car might have one velocity and then a different velocity later on. Depending on the instant, that is your instantaneous velocity.

An example of both velocities in my life are here:

>Average velocity: When I run some where like say down a hallway my velocity does not stay the same and usually I would focus on my average velocity. I do not run the same rate the whole time so I would take a few of my velocities while running and divide it by the number of information to get my average velocity. I would also take note of the direction.

Also, sometimes when dancing the velocity of my movements change (if that counts). And while someone drives their velocity changes.

Maybe riding a bike or something can also represent average velocity. I don't ride a bike any more, but I definitely did ride one a lot when I was younger.

>Instantaneous velocity: In my own life I guess when I use the treadmill I take note of my instantaneous velocity. Or I at least show instantaneous velocity. The reason why is because at a given moment you usually have your settings at a certain speed and what not. So for 10 minutes I could be running at the fourth speed reaching a distance of half a mile or something. Once the velocity is solved for that would be the instantaneous velocity for that one moment.

Plus, with each of my activities like biking, running, or dancing instantaneous velocity would be one instant from each of those. Unlike average velocity, you are only focusing on one given velocity at one given moment in time.

Also, here are some graphs of velocity and speed: 

And also here's how to use the equation for speed and velocity:

s = d/(change in t) and v = change in x/change in t
s = 2000 m/100 s          v = 100 m - 0 m/ 50 s - 0 s
s = 20 m/s                      v = 100 m/50 s
                                       v = 2 m/s (+ a direction)

But enough of my blab, good night everyone :33.