Answer: the third option, a change in velocity over a period of time.
Justification:
The concept of acceleration always is related to a change in velocity.
That change may be either on speed or on direction or both.
The mathematical definition of acceleration is:
change in velocity final velocity - initial velocity
acceleration = ----------------------------- = ---------------------------------------
interval of time Δt
We can go through the list of choices to check their validigy:
- a change in position over a period of time: this is velocity definition
- a force applied over a
displacement : this is not a defined magnitude
- a change in velocity over a period of time: this is exactly what acceleration means.
- a force applied
for a period of time: this is is not a defined magnitude.
