Displacement, distance and average speed
Displacement compares endpoints; distance measures the travelled path.
Key knowledge
Displacement is the final position minus the initial position in a stated frame. Distance is the length of the travelled path and is at least the displacement magnitude. Average velocity is displacement divided by elapsed time; average speed is distance divided by that time. A round trip can have zero average velocity and positive average speed.
Values and equations
Δr=r_f−r_i; v_average=Δr/Δt; speed_average=s/Δt; s=∫|v(t)|dt
- r_i,r_f,Δr,s
- Initial/final position, displacement and path length m
- v,v_average,speed_average
- Instantaneous vector velocity, average velocity and average speed m s⁻¹
- t,Δt
- Time and positive elapsed time s
Conditions and scope
- Use one stated reference frame and a positive elapsed time.
- The integral for distance assumes a differentiable or piecewise smooth trajectory; speed is the magnitude of instantaneous velocity.
Sources · 1
References
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Evidence and review
Read §3.1 Position, Displacement and Average Velocity definitions and worked round-trip/path distinction. Vector notation and the path-length integral are disclosed extensions using the existing velocity definition; no new trajectory theorem is claimed.
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Entry details
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- foundation-physics-displacement-distance
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- foundations-refresh.1
- Structured reference record
- Foundational reference additions