Hi everyone!

[Before to ask for help I would like to say "I don't speak English very well" because English is not my mother tongue , so if I make a mistake writing I'm really sorry ]

I have a question about Average velocity formula because there are two formulas and I don't know which one use for to solve problems and why there are two, The formulas are:

Average Velocity= V1+V2/ 2
Average Velocity= X-X0/T-T0

Why there are two formulas? What is the difference between the first one and the second one?


Thank you very much !

Have a nice day!

Do they give a different result? There could be two formulas, since "Velocity" is a calculated quantity. Velocity is not something that can be directly measured.

There are two different formulas because there are two different states of knowing things.

And you have made a huge error in not writing down the parentheses or the conditions.

For constant acceleration, A, we have

X = X0 + V0 (T − T0) + (1/2) A(T − T0)²
V = V0 + A (T − T0)

So
X1 = X0 + V0 (T1 − T0) + (1/2) A(T1 − T0)²
V1 = V0 + A (T1 − T0)

So
(V0 + V1)/2 = ( 2 V0 + A (T1 − T0) )/2 = V0 + (1/2) A(T1 − T0) = (X1 - X0)/(T1 − T0)

So when acceleration is constant, the average of the instantaneous velocity at times T0 and T1 is (V0 + V1)/2, and this is equal to the net distance traveled (X - X0) divided by the elapsed time (T − T0).

Thus the average velocity that the object moved at is the average of the instantaneous velocities at the end points -- as a consequence of the acceleration being constant.

As for Robittybob1's claim that velocity is not something that can be directly measured, that is not a well-supported position and has nothing to do with the physics that you are trying to learn.