Question

Question about average velocity:
I can understand why 'average velocity' equals change of distance/ change of time.
mathematical equation: average velocity= average distance/average time. v=d/t.

What I don't get is "Why is 'average velocity' also equal to initial velocity + final velocity over 2?"
mathematical equation:
average velocity = (Vi + Vf)/(2).

Answer 1

Do you want to know where did the "...mathematical equation: average velocity = (Vi + Vf)/(2)..." came from? Or are you looking for a physical interpretation of average velocity ??

Answer 2

I am looking for the 1st question you asked me. I get the physical interpretation of average velocity. Your help would be great.

Answer 3

"...mathematical equation: average velocity = (Vi + Vf)/(2)..." is applicable only when acceleration is constant.

For proof, consider a v-t graph with constant acceleration (hence straight line). Calculate average velocity using "...'average velocity' equals change of distance/ change of time..."

Note that the total displacement would be the area under the graph.

I leave the rest as an exercise. :)

Answer 4

Consider this as barter system :)
Please explain the meaning of "정현돈" in English.

Answer 5

Thank you for your answer. ^^
I am not quite sure of it's meaning. The characters are in Korean, and its meaning is derived from Hanja.

Answer 6

Just for my future reference. http://www.khanacademy.org/science/mcat/physical-processes/acceleration-mcat/v/average-velocity-for-constant-acceleration

Answer 7

What LastDayWork wrote:
"...mathematical equation: average velocity = (Vi + Vf)/(2)..." is applicable only when acceleration is constant."
is very important.

In no case is this equation a universal one. It is only a useful trick to express average velocity and distance travelled during a given time interval when acceleration is constant.

What I want to say is that this equation is useful if you have to solve small problems with multiple choice answers in the context of a competition where you have to be as fast as possible.
On the other hand, it is of no use for your true understanding of the concepts in mechanics.

Answer 8

@정현돈
Please consider closing the question.

Answer 9

Thank you for a good insight, Mr. Lyon.Fr. Your explanation excels for my understanding and my studies.