This is where things start to get a little tricky, so bear with me and read things several times if you have to.
Okay, in order to get the first equation, an equation has to be assumed. This equation is:
Basically what these equation represents is Acceleration. Acceleration equals the change in velocity over the change in time. These make sense if you think about it. When you watch a car drive away, it's velocity is measured by the amount of distance it covers over the amount of time it takes. That being said; when you watch the same car drive away, the acceleration of the car can be said to be the change of the velocity over the amount of time it takes.
To make things easier on yourself, next assume that in your two equations, ti is always 0. This means that you can drop that term. So now you're left with:
Now I'm going to do some algebra to make this equation a little easier to read and deal with. First I'll take the t over to the other side.
Next I'm going to take the Vi over so that there are no negatives and you can solve for the final velocity a lot easier. The final equation then looks like.
| (Note: this equation only works when the acceleration is constant. If the acceleration is not constant, then you will have to recalculate the equation for every time the acceleration changes.) |
Did you follow all of that? I'm sure you did. Now you're ready to move on to the second equation.