How To Calculate Velocity
This video is a short, informative lesson on how to calculate velocity presented by a math tutor from London. He gives easy to follow, step by step explanations of two different methods of determining velocity and provides formulas as well.
In this video, I am going to show you how to calculate velocity. Now, there are two ways of calculating velocity. The first way is the easy way and the second way is slightly harder.
So, the first way is velocity. What's the difference between velocity and speed? Now, velocity and speed are often quoted the same thing, but actually they are different. Velocity is different to speed in that velocity needs two things.
One, it needs the size, that is your speed, and secondly, it needs a direction. So, whenever you're asked for the velocity, you need to quote two things, the size of it, i.e.
the speed, and the direction. So, there's a difference. If I am travelling up the motorway at seventy miles an hour in the northbound direction, then my velocity is seventy miles per hour, that's my speed, in the northbound direction.
If I am travelling southbound, then my velocity is seventy miles an hour, but southbound. So, there is a difference, as the two are actually different, although the speed is the same, the velocity is different because they're travelling in different directions. So, you must always quote two things when asked for velocity.
Now, how to calculate velocity. Well, velocity is your speed, essentially. That's what you need to find out.
The direction is often obvious. It's just the way you are heading. You need to find the speed.
Now, speed is basically distance you travel and the time you travel it. So, basically, velocity, or speed, is the distance you travel divided by the time. Okay, so let's say I travel from here to Birmingham, so that is a hundred miles and I do it in two hours.
So, I travel a hundred miles in two hours. That means my velocity is, for every two hours, I travel a hundred miles. So, in one hour, I travel fifty miles.
So, that's my velocity - fifty miles per hour is my velocity. Now, often, we don't really use miles per hour, we actually use meters per second. So if you're travelling a hundred meters, so if you run a hundred meters and you run it in ten seconds, then your speed, or your velocity, is ten meters per second, and that's how we write meters per second.
Meters per second, S to the minus one. That's how to calculate velocity easily. Now, there's a second way to calculate velocity.
Let's say you're given an initial velocity and you're given an acceleration. So, see, this time, rather than moving at a straight speed, you are actually accelerating. So, let's say I start travelling, and I am running and I run past a start line.
Let's say I am running at ten meters, I can't run that fast so let's say five meters per second, okay, and then I start accelerating, I try and run a bit faster. Let's say, my acceleration is two. That's how we write acceleration.
So, this means for every second, I am increasing my speed by two meters per second. So, one second later, I'll be travelling seven, the next second, nine, and the next, eleven, etcetera. And let's say, I start doing that for just two seconds.
Okay, so I accelerate at this rate for two seconds, but I start at this speed here, five meters per second, so I started a jog and I start accelerating but I only accelerate for two seconds. We use this equation v=u plus a t. This says that my velocity, my initial velocity, plus my acceleration times the time.
So, my velocity, my initial one, that's five, plus my acceleration, that's two. The time I do that for, that's two, so my velocity is five plus four, which is nine. We always write the unit meters per second.
And that's how to find velocity.