Homework Clinic
Mathematics Clinic => Grade 9 Mathematics => Topic started by: mydiamond on Oct 4, 2013
-
Starting speed: 89.6 mph
Ending speed: 77.7 mph
Distance travelled: 55 feet
How can I calculate the time in flight?
Is it possible to make an Excel formula so I can just plug in the numbers?
-
Well, you know distance, v1, v2, and acceleration.
Try this equation:
d = t*(v2-v1)/2
Isolate for t.
-
Sure. Start with the basic position/acceleration formula:
x= v0(t) + 1/2a(t^2)
x=55/5280 (to put it in miles), v0=89.6, and a=average acceleration = change in velocity/change in time = 11.9mph/t
pump these in the formula and you get
55/5280 = 89.6t + (5.95/t)(t^2)
55/5280= 89.6t + 5.95t
Notice that the nasty t^2 term gets taken care of by the /t you carried in from the a formula, so rearrange this to isolate t and you have your answer:
(55/5280)/(89.6+5.95)
The excel formula should look like this:
(distance in miles)/(starting speed in mph + 1/2 the change in speed in mph) = time in hours.
I'll assume you can do the unit conversion if you want this is seconds, and since you're going to code this I won't bother to punch the calculator for you.