Worked example
A gauge rises from 13 to 19 cm over 30 minutes. The change is 6 cm and the duration is half an hour, so the average is 12 cm per hour. A different gauge rises by 9 cm in an hour. Its larger total change comes with a smaller hourly rate.
Contrast and common error
An hourly equivalent describes the average over the observed interval. It does not say the gauge would rise by that amount during the next hour. For an overall rate across intervals, divide the combined change by the combined elapsed time; use a simple average of rates only for equal-length intervals.
Transfer check
A tank gauge shows 7 L at minute 4 and 19 L at minute 10. A second tank gains 10 L over 5 minutes. Compare average rates. Check: 12 ÷ 6 and 10 ÷ 5 both give 2 L per minute.
Try it, then explain it.
Complete a short set without looking at the example. After each answer, explain which evidence or rule supports your decision and why the alternatives do not fit.
Sources & authorship
Original OpenExam explanations and examples. References support the concepts; they are not the source of copied questions. Independent educator review is pending.
OpenStax Physics 2.3 Position vs Time Graphs