PETER BRUCE - Eastchurch Gap Posted May 18, 2017 Share Posted May 18, 2017 Not For The Faint Hearted... Quote Link to comment Share on other sites More sharing options...
PETER BRUCE - Eastchurch Gap Posted May 18, 2017 Author Share Posted May 18, 2017 And Now For The Quiz - Read On. So you all know - My elastic band trick to hold the camera on the plane finally broke and the little camera took a tumble from about a hundred foot. I wonder if anyone can work out the exact time the camera was in free fall and hence tell us all the height. There's an interesting challenge Quote Link to comment Share on other sites More sharing options...
Don Fry Posted May 18, 2017 Share Posted May 18, 2017 Not if you can supply the coefficient of friction for the camera. Otherwise bets off. Quote Link to comment Share on other sites More sharing options...
Don Fry Posted May 18, 2017 Share Posted May 18, 2017 Nice film by the way. Loved the shot of the departed plane. Quote Link to comment Share on other sites More sharing options...
PETER BRUCE - Eastchurch Gap Posted May 18, 2017 Author Share Posted May 18, 2017 Thats hard... Size is 115 x 40 x 40 mm other than that a good guess could be good enough but its not an easy shape and it truly helicoptered all the way down... Quote Link to comment Share on other sites More sharing options...
PETER BRUCE - Eastchurch Gap Posted May 18, 2017 Author Share Posted May 18, 2017 Here is the camera - 115 x 40 x 40 = Any takers now! Quote Link to comment Share on other sites More sharing options...
Mike Etheridge 1 Posted May 18, 2017 Share Posted May 18, 2017 Not sure you can use the simple equations of linear motion Pete as the pilot is falling from a height, I cannot remember any others. S= UT + 1/2 FT squared V squared = U squared + 2FS V = U + FT (Needs checking) We only have S which is 100 feet, we do not have U which is the initial velocity or V the terminal velocity, F being the acceleration due to gravity at -32 feet per second per second as it is a deceleration. Any chance of flying at the club this weekend? Edited By Mike Etheridge 1 on 18/05/2017 16:36:57 Quote Link to comment Share on other sites More sharing options...
PETER BRUCE - Eastchurch Gap Posted May 18, 2017 Author Share Posted May 18, 2017 Hi Mike& all... It was flying down wind on half throttle so lets call it around 27 mph and the "pilot" would fall in an arc at first till it got to 32 fpsps. I can only assume 100 feet as that was only my guess however if someone can do the math it would be interesting to see how far I was out on height! What we do have is the exact time the pilot left the plane to the time he hit the ground. Please note the "Bounce" don't count in the time... The margin of error cant be that much as the numbers a times of the fall are not great. I know there are variables - so whos going to come back first - if any - I wonder... PS Sunday looks the best so far - fingers crossed Mike... Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted May 18, 2017 Share Posted May 18, 2017 Surely the linear velocity can be largely ignored (there might be some lift generated but it's not going to be significant) and the acceleration due to gravity will be from zero, assuming level flight. Quote Link to comment Share on other sites More sharing options...
onetenor Posted May 18, 2017 Share Posted May 18, 2017 From the length of time of the fall it would seem that the fall was a lot higher than 100 ft or the helicoptering fall slowed it down.I Timed it loosely at about 7 seconds even averaging the speed at 30 fps that is 210 ft. Is it likely you could have been that high? Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted May 18, 2017 Share Posted May 18, 2017 210 feet isn't very high when observed with the aid of onboard telemetry - I couldn't get the video to play to check your timing but but isn't the theoretical figure 1/2gt2 - roughly 10 x 7 x 7 divided by 2 = 245m in metric units or around 750 feet? Knock off a little for the rounded up G figure and air resistance and I suspect it was still over 600 feet. Quote Link to comment Share on other sites More sharing options...
PETER BRUCE - Eastchurch Gap Posted May 18, 2017 Author Share Posted May 18, 2017 This is interesting - Firstly I have to say I was watching as best I could Both the plane and camera fall so my estimate at 100 foot was a pure guess. I also reckoned around 7 seconds for the fall but some of that time it would have been traveling along horizontally which can be seen as its falling in line with the plane but it still means my 100 foot estimate was well out. Some years ago I had an on board camera fitted to a Calaris I was chugging around and I was thinking I was flying along the beach / seashore when in fact I was a long way off shore. Seems easy but its not and trying to keep tabs on both the falling camera and the plane makes my estimate way out - I wonder if anyone can be anymore specific just using the data that's available from the video... Interesting this... Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted May 18, 2017 Share Posted May 18, 2017 I'm sure you can disregard the horizontal velocity - see here for apparent confirmation... Any proper physicists out there? Quote Link to comment Share on other sites More sharing options...
brokenenglish Posted May 18, 2017 Share Posted May 18, 2017 Posted by Martin Harris on 18/05/2017 20:36:23: Any proper physicists out there? No, but there's an old Navigator (Bomb Aimer), watching with amusement... Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted May 18, 2017 Share Posted May 18, 2017 I'm sure we'd appreciate his input... Quote Link to comment Share on other sites More sharing options...
PETER BRUCE - Eastchurch Gap Posted May 18, 2017 Author Share Posted May 18, 2017 Perhaps our ex bomb-aimer can throw some light on the subject... Quote Link to comment Share on other sites More sharing options...
McG 6969 Posted May 18, 2017 Share Posted May 18, 2017 I'm personally not a physicist nor a bomb-aimer at all (well... ?!) , but isn't this simply the old Newton 'apple' stuff? Having 7 seconds of 'dive/fall' at 9,81m/sec, would equal to a height of 68,67m (or 225 ft) as linear horizontal velocity has nothing to do with it as Martin already stated. Cheers Chris Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted May 18, 2017 Share Posted May 18, 2017 Acceleration due to gravity isn't linear though - until an object reaches terminal velocity (drag equal to force exerted by gravity) it continues to accelerate with the square of time (ignoring drag which also increases similarly). At least, I think that's what my physics teacher told me - and I think he was old enough to have got it from that nice Mr Newton... Quote Link to comment Share on other sites More sharing options...
McG 6969 Posted May 18, 2017 Share Posted May 18, 2017 ... well, apologies then, Martin. ... next time, I'll just sit under the tree watching the cameras falling... and remain silent... Cheers Chris Edited By McG 6969 on 18/05/2017 21:36:53 Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted May 18, 2017 Share Posted May 18, 2017 I could be wrong - it was a very long time ago! Where's a bomb aimer when you need one? Quote Link to comment Share on other sites More sharing options...
PETER BRUCE - Eastchurch Gap Posted May 18, 2017 Author Share Posted May 18, 2017 Looks like I could have been out by 100% = Ouch Quote Link to comment Share on other sites More sharing options...
PETER BRUCE - Eastchurch Gap Posted May 18, 2017 Author Share Posted May 18, 2017 Perhaps I was so wrong with my height estimate because it's a big model! Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted May 18, 2017 Share Posted May 18, 2017 I fly my >7kg models with an altimeter - we have a 400' height limit for them and it's just enough to do a decent loop... Quote Link to comment Share on other sites More sharing options...
Mike Etheridge 1 Posted May 19, 2017 Share Posted May 19, 2017 So height = 100 feet (S) initial Velocity = 27 MPH = 36 Feet per second ( U) Using the equation V Squared = U squared + 2 F S Then V Squared = 36 squared + 2x32x100 V Squared = 1296+6400 V = 87.72 Feet per second. Using the equation V=U +FT Then T = 87.72-36/32 T = 1.61 Seconds First time I have done one of these calculations since 1965---the height could be wrong Pete and hence this calculation! Quote Link to comment Share on other sites More sharing options...
PETER BRUCE - Eastchurch Gap Posted May 19, 2017 Author Share Posted May 19, 2017 Hi Mike. WoW. Looks like you cracked it and I crapped it with my estimated height. Does this mean I will now be scolded Sunday. Think me needs an altimeter... Quote Link to comment Share on other sites More sharing options...
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