# Question regarding velocity

if you were to look at a "freeze frame" of time (i.e. a movie that's been paused)

and you saw a baseball in the air. how would you know that it had a velocity??

i mean, a baseball is a collection of atoms. how would you know, just by observing it, that it has a velocity (and what velocity? can you tell?)

At each moment in time, each object must have an "instantaneous velocity". How do you explain that in terms of the atomic scale??

you wouldn't. unless somehow you were able to measure the objects energy level (mass) and knew beforehand its energy (mass). it would be completly immpossible given our current technology becuase the change in mass (energy) would be so small.

Originally posted by brum
if you were to look at a "freeze frame" of time (i.e. a movie that's been paused)

and you saw a baseball in the air. how would you know that it had a velocity??

i mean, a baseball is a collection of atoms. how would you know, just by observing it, that it has a velocity (and what velocity? can you tell?)
As maximus said, you would not be able.
(techniclally, each frame of the moive took about 1/24 of a second, so there is what is called motion blur that allows you to know an approximate value of the velocity, but i am sure this is not what you are looking for).

At each moment in time, each object must have an "instantaneous velocity". How do you explain that in terms of the atomic scale??
(I don't really understand what do u mean by "in term of atomic scale" here).
Well, we also cannot know the instantaneous velocity from only a single snap a the object in a certain moment, in order to know the instantaneour velocity we normally need to have a graph of displacement against time, if we only have a single point of the graph (ie, a single snap about the object), we will not be able to calculate its instantaneous velocity.
What we do to calculate the instantaneous velocity is that we study the behaviour of the graph near the point of interest using calculus, then from the info we get about the object just before and just after the point of interest, we can know its instantaneous velocity.
You can think of it (although this way is not perfectly right, but for the moment it might help) as calculating the velocity on a very small interval, say 10-1000 seconds, you will get a value of the velocity that you can almost call instantaneous (but it is not, remember, to calculate the instantaneous velocity you need to use calculus).
If you already know some calculus, let us help you know how to use it to find instantaneous velocties.

I hope i helped .

edited for formatting mistake.

Last edited:
LURCH