How this instrument works
Average velocity is the plainest measurement in kinematics: ground covered, divided by the time it took. The formula v = d ⁄ t makes no claims about what happened along the way — a sprinter exploding out of the blocks and a train holding a steady cruise can post the same average if they cover the same ground in the same interval. Its strength is exactly that modesty: it needs only two measurements anyone can take, a length and a stopwatch reading.
Because the relation is a single division, it rearranges without loss. Multiply back and d = v·t recovers the ground covered when pace and duration are known; flip the division and t = d ⁄ v predicts how long a stretch will take. Schoolbooks draw the three quantities as a triangle with d on top; this instrument gives each corner its own dial position instead, so the working shown always matches the quantity being solved.
Units do the quiet work here. The arithmetic runs in metres and seconds, and every displayed figure is converted on the way in and out — so 60 miles in 1.5 hours and 96.56 km in 90 minutes are the same problem in different clothes. One exact factor worth memorising: multiply metres per second by 3.6 to get kilometres per hour, because an hour holds 3600 seconds and a kilometre holds 1000 metres.
- Pick the mode on the dial: Solve v, Solve d, or Solve t. The field being solved becomes the answer and stops accepting input.
- Enter the two known quantities — Distance, Time, or Velocity, depending on mode — choosing units from each field's own menu.
- Read the Result line, shown to three decimals; switch its unit between m/s, km/h, and mph without re-entering anything.
- If a check flags a negative Distance or Time, correct the sign — this sheet computes magnitudes, not directions.
Worked example — the fastest 100 metres ever run
Berlin, 16 August 2009. Usain Bolt covers 100 m in 9.58 s — still the world record. Set the dial to Solve v, enter 100 in Distance and 9.58 in Time: v = 100 ⁄ 9.58 = 10.438 m/s. The unit menu restates that as 37.58 km/h, or 23.35 mph — highway pace, on foot.
The average hides the shape of the race. Bolt touched roughly 12.4 m/s at mid-race peak; the 10.438 figure blends the costly first strides out of the blocks with everything after. That is the honest limitation of v = d ⁄ t, and exactly why sprint coaches keep split times.
Questions
Is velocity the same thing as speed?
Strictly, no — velocity is speed with a direction attached, and it can be zero even while the odometer climbs, as on a lap that ends where it began. This sheet works with magnitudes: total ground covered over elapsed time, which physics calls average speed. For straight-line, one-way motion the two coincide, and that is the everyday case the instrument is built for.
How do I convert m/s to km/h or mph?
Multiply metres per second by 3.6 for km/h — the factor is exact, since an hour holds 3600 seconds and a kilometre 1000 metres. For mph, divide metres per second by 0.44704, also exact by the international definition of the mile. The Result field's unit menu applies both conversions for you.
Why does Solve t give no answer when velocity is zero?
Because t = d ⁄ v divides by the velocity, and division by zero has no finite value — an object that is not moving never arrives. The sheet leaves the result blank rather than inventing a number. Enter any nonzero pace and the time appears at once.
Does this account for acceleration or stops along the way?
No — v = d ⁄ t sees only the endpoints: total ground covered and total clock elapsed. Red lights, rest breaks, and pace changes are averaged in silently, which is why a road trip's average sits noticeably below the cruising figure on the speedometer. For motion with constant acceleration, a kinematics sheet with an acceleration term is the right instrument.
What was Usain Bolt's average speed in the 100 m world record?
10.438 m/s — 100 metres in 9.58 seconds, Berlin 2009 — which converts to 37.58 km/h or 23.35 mph. His peak, measured over the 60–80 m split, was around 12.4 m/s; averages always sit below peaks because the start costs time that the finish never repays.