Quick answer
Average velocity = Δposition/Δtime on an interval.
Formula
- (s(b) − s(a))/(t(b) − t(a))
Introduction
Replace f with position and x with time on the interval you measure. The algebra is the same; the nouns change.
Solidify the math with motion examples that show subtraction before unit labels.
When your lab report asks about speed at an instant, compare with calculus and limits ideas for instantaneous rate.
Plot data in the Average Rate of Change Calculator to show a secant slope alongside your measured points.
Motion meaning
Average velocity summarizes net displacement change per unit time across the whole interval.
Negative rates mean position decreases along the chosen axis direction over that window.
Units such as m/s or ft/s must appear in the final statement.
A curved position graph still uses endpoint times and positions unless the problem defines another interval.
Formula in motion notation
- Δs/Δt
- (s_final − s_initial)/(t_final − t_initial)
Use consistent reference frames. Changing direction mid-interval affects displacement, not just distance traveled.
Distance traveled and displacement can differ when the path turns; read the question carefully.
- Draw a diagram. Mark start and end times and positions on a line or axis.
- Choose interval endpoints. Use the times the problem names, not the largest speed moment inside the trip.
- Compute Δs and Δt. Subtract in matched order, then divide.
- Interpret sign and units. Explain whether motion is forward or backward relative to your axis.
Trip example
Position 0 m at 0 s and 20 m at 4 s gives Δs = 20 m, Δt = 4 s, average velocity 5 m/s.
If the object returned partway, displacement endpoints might differ from total path length.
State clearly that 5 m/s is an average over 0 to 4 s, not the speed at every instant.