How is speed calculated on the app?
- Posted in: Drills, Mobile App
Both the Dash and Flying drills allow you to enter in a distance when connecting your lasers. When you include a distance, speed will be calculated. Here are some details on how it is calculated.
Speed is the change in distance (Δs) divided by the change in time (Δt).
Speed = Δs/Δt
This calculation gives you the average speed over the distance measured. So if you are doing a 10 yd dash from a static start, your starting speed is close to zero and your finish speed is much higher – this calculates your average speed over those 10 yards.
A 40 yard dash example is pictured below, along with a screenshot of timing in the app. This is a 40 yd dash with a 10 yd split. In the app this is indicated by a “10/40 yd Dash” at the top. The time presented for the 10 yd split is the time from the start to the 10. Similarly, the time presented for the 40 yd finish is the time from the start to the 40. The speeds associated with these times are the average speeds over those distances. As expected, Caleb here got faster as he covered more ground.
To work out this calculation lets calculate it as yards per sec and then convert to MPH.
For the 10 yd split – Δs=10 yards and Δt=1.93 sec. Δs/Δt = 5.18 yd/s
There are 1760 yards in a mile and 3600 sec in an hour, so to convert to MPH we multiply 5.18 yd/s by 3600/1760 (or 2.045).
5.18 yd/s x 2.045 (miles x s)/(yd x hr) = 10.59 MPH which rounds to 10.6 MPH.
For the average speed for the whole 40 yds, Δs=40 yards and Δt=5.04 – repeat the calculation.
For the flying set-up, note that the distance inputted for the start laser is the approach distance. If you are doing a 10 yard fly with a 20 yard approach (or run-up) then the start distance would be 20 and the finish distance would be 10. The speed is calculated from the start laser to the finish. On the testing page this is indicated as “20/10 yd Flying” at the top. So for Caleb’s example below Δs=10 yards and Δt=1.11 sec, Δs/Δt=9.01 yd/s – multiply that by the 2.045 value and you get 18.42 MPH rounded to 18.4 MPH.
