Anybody got a laser tachometer lying around?

Height is quite easy to work out, if you want to know that. S=ut+1/2at^2. Which means if you time the compleate flight time of you diabolo you can work out how high it went.The deceleration of the diabolo going up and the acceleration of the diabolo going down are the same, ingoring the bit where you fling it right at the start. Which means time going up is equal to time going down. Acceleration is 9.81ms^-1 and u=0 when at the top of the arch. So input your flight time divided by 2 and that'll give you the height. The error is huge, like 20% because of the timing and ignoring the bit where you fling it.example, 20 seconds for up and down. gives t=10s u=0 a=9.81ms^-1s=0*10 + .5*9.81*10^2 =0 + 490.5mSo that'll be nearly 500m.