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rocket,model,launch,fail Rocket's parachute fails to open, narrowly misses spectators
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Hmm.. I wonder if you need to know how strong the propulsion was, and/or the mass of the rocket to figure that out, or if the time of ascent and descent is enough?
I guess that approximately half of the time it spent ballistic was falling, so lets say that it was falling for 12 seconds. (Total guesstimation here, of course)
Accelleration due to gravity is 9.81 m/s*s so that's ... 117 m/s which according to google calculator is 421km/h. For the yanks in the audience that is 262mph.
That's assuming that its terminal is higher then that, and that my guesstimation about falling for 12 seconds is right.
... On second thought, I bet it was falling even longer. Maybe 13 seconds. The rocket goes up with the engine on for 6 seconds, but who knows how high it got? It seems to me that without knowing what to put in for propulsion and mass, you can't figure that out. Once the engine cuts out, at 18 seconds into the video, it turns into a normal projectile... with a very high velocity. It now will spend an equal time going UP and coming back down to that unknown height where the engine cuts out.
Hmmm... disregarding air resistance, terminal velocity and all those messy things, I seem to recall that the rocket will now be travelling downwards at the same velocity that it was hurtling towards the sky... Does that mean that we can make a guess as to how many seconds it will take to fall from that height? I bet that a reasonable guess could be made, if we make some assumptions about how much force the propulsion exerted on the rocket.
Hum, I wish my wife was awake right now, she'd whip up a diagram and do the calculations and tell me what kind of assumptions we would have to make, and everything.
Just to have an idea though, if it fell for 13 seconds, the velocity of impact becomes 457kph and at 14 seconds it would have been 493kph.
No wonder it made a screaming sounds. Whoa.
I like the screaming sound it makes just before! Any physicists in the crowd care to work out how fast it was going? Assume that the rocket's energy expenditure was totally linear and lasted exactly 6 seconds.
Hmm.. I wonder if you need to know how strong the propulsion was, and/or the mass of the rocket to figure that out, or if the time of ascent and descent is enough?
A rough formula for the fall of the rocket would be
v = g*t - 0,5*t*c_w*A*p*v^2
The stuff behind the g*t would be the air resistence. You should consider this at high speeds like 450 kmh.
So. If you solve this to get v you would get something like this
v = - m/(c_w*A*p*t) +- sqrt( (m/(c_w*A*p*t))^2 + (2*m*g)/(c_w*A*p) )
Please correct me if I'm wrong. I just wrote a test about dynamics and I didn't get the results back yet - so maybe I failed which means I suck.
c_w = 0.1 (air drag coefficient for a rocket)
A = 0.07 m^2 (estimated value for the area of the rocket if you would look directley into it)
p = 1.2 kg/m^3 (air density)
m = 50kg (I don't know how much it weighs... 50kg??? *shrug*)
t = 13s
If you calculate that you'll get 113 m/s or roughly 400 kmh. Hm thats very interesting, I would have thougt that the air resistence would be much higher. But 50 kmh less is still a bit.
The rocket's total time in the air = t
Inertia = i and of course speed = s
You find the final impact is directly related to the rocket's point of origin = o and the height it achieved resulting in
o+h=(s*h)(i/t)!
>> ^Gabe_b:
holy f ing s t, Batman.
boring.