This one has come up before on the internet, and I don’t get it at all. I don’t know alot about physics, but how could an average velocity of anything ever be 0. Wouldnt that only be possible if the object hadn’t moved at all? or does velocity have a different meaning than speed here?
In: Physics
Veloxity is directional, a vector. Speed has no direction just values and is a scalar.
The magnitude of the velocity is the speed.
If you walk in an east-west corridor the velocity in one direction might be 2m/s east. When you walk back might be 1m/s west.
The corroded might be 20-meter long so 10 for the moved to east and 20s to the west
If the positive direction is east and negative west. so a +2 velocity east and a -1 west
Average velocity is (2*10+(-1*20))/30 =(20-20)/30=0/30 =0
That is a 1D example but it works the same in 2D and 3D. So the average velocity if you return to the same spot has to be zero.
All this is relevant to the surface of the earth, so it is true in that reference frame. But on another sun centric reference frame earth rotate around its axis and around the sun, The sun orbit the center of the galaxy. The galaxy moves towards the great attractor. All reference frames are equally valid but more or less useful.
So if the statement is true depends on what you measure velocity relative too. You can always measure it relative to yourself and you are always stationary. It is as valid as all other but most of the time a lot less useful
Speed is distance travelled/time elapsed.
Velocity is speed in a given direction.
So, velocity can be -10mph for example.
That means if you walk forwards at 10mph for a given distance then walk backwards at the same speed (-10mph velocity) then your average velocity is 0mph. (even though your average speed is 10mph).
Using this analogy for being born and dying in the same place is just a lot more complicated than travelling in a straight line forward and back, but essentially all of your lifetime’s movements counter each other.
Velocity is defined as *change in position over time* (as in the units: meters per second). Speed is just velocity *without a direction*.
Since there must be a nonzero change in position for a nonzero velocity, you can say that if an object moves and then returns to its original location, it has an average velocity of zero over the entire timespan of the scenario.
Using the original position as an origin (zero) and defining position as positive in all directions away from that point, velocity when moving away will also be positive; moving back toward the origin will give negative velocity. Returning to *exactly* the same position will yield exactly equal positive and negative velocities for each unit of time passed over the whole process — giving zero.
So, glibly, if you returned to the exact place in the hospital where you were born and then died without moving, you might say you had an average velocity of zero over your life — relative to a resting frame of the Earth and ignoring all other movements (e.g. of the tectonic plate on which the hospital sits, the foundation of the hospital, etc.). It does not really mean anything particularly useful or important, though.
Latest Answers