what are you doing ?

[Ray P]

Wisteria can (and will) eat you out of house and home!

We've got one of the smaller varieties for that very reason and the growth is quite manageable though the price is smaller flower panicles (but still beautiful). I don't remember the variety off-hand - would need to check.

[Mike H]

You need compost bins Phil

Yes, but no.

Thing is, I don't grow anything, so what would I do with the compost ?

Suggestions please.

Is there an allotment nearby, something like that? They could have it.

[jack]

Made a MONSTER potato cannon with #2 son (the other engineer)... It's his cannon and his design.

Shot a tennis ball so high it took 7 seconds to come back down

Fuel/air mix (Treseme hair spray) and a piezo igniter from a BBQ lighter.

Tried to video it - sound is awesome but the tennis ball is so small it doesn't show up. Video is OK though!

Gave the buzzards circling in the thermals over the hill something to worry about...

[pre65]

Made a MONSTER potato cannon with £2 son (the other engineer)...

You had to buy a son ?

[jack]

Made a MONSTER potato cannon with £2 son (the other engineer)...

You had to buy a son ?

Yep. Already had one but needed a spare (hoarding really).

SWMBO says we have to stop firing the cannon as the pets are wetting themselves...

Plus we've run out of tennis balls...

It does sound completely awesome though

[andrew Ivimey]

You'll be using spare son and or pets next...

Seven seconds, how far up (& down) is that?

[Nick]

You'll be using spare son and or pets next...

Seven seconds, how far up (& down) is that?

60m up (I cheated https://www.omnicalculator.com/physics/free-fall)

[ed]

60m up (I cheated https://www.omnicalculator.com/physics/free-fall)

are you working on the premise that it was a 3.5 second journey each way?

[Ray P]

Based on the imprecise information available, Nick arguably only specified the time it took to come back down, not how long it took to go up,

Shot a tennis ball so high it took 7 seconds to come back down

the zenith of the trajectory was at a height of 240m according to the calculator, and that's not considering the atmosphere the ball is travelling through.

More information required to properly calculate the trajectory.

[Nick]

Shot a tennis ball so high it took 7 seconds to come back down

I am rather sure that this slight imprecise sentence is describing the total flight time not only the time it was travelling towards the ground. It also seemed for the purposes here valid to ignore drag, in which case the time up would equal the time down. Therefore I found the distance a mass would travel if dropped for 3.5 seconds.

[ed]

Based on the imprecise information available, Nick arguably only specified the time it took to come back down, not how long it took to go up,

Nick's post came after Andrew's, which included :

Seven seconds, how far up (& down) is that?

so given that sequence of posts why would he 'arguably' specify only the time it took to come down?

I ask because it's plain to me that the tennis ball would be subject to extreme initial acceleration and would not be constrained by terminal velocity, whereas the return journey would commence with sedate initial acceleration and be subject to terminal velocity, what with all the atmospheric interference messing with the suck of gravity. For some reason I rather thought the return journey would not be quite the same as the outward journey......and I thought Nick may have considered this, or maybe not, hence my question.

[IslandPink]

You are correct Ed, I regarded Nick's estimate as a first-order approximation... what do we do for the 2nd-order correction ?

[jack]

Total flight time from launch via re-entry to touchdown = approximately 7 seconds.

Projectile was a carefully aged (the dog chewed it) tennis ball with a worn nap (and probably residual dried drool), so fairly high drag coefficient (but not as high a a new ball). All propellant charges were standard 3-second TRESemmé Botanique Natural Hold fuel/air mix.

Launch trajectory was pretty much vertical, though the wind (from the SW @ 8km/h) caused descent horizontal drift and consequential unplanned impact on a neighbour's roof.

Must find a way to upload the video though that is for a 5 second, sub-orbital, flight but you can see the muzzle flash. Again, into a neighbour's... Other trajectories included low elevation, low vertex, i.e. flatter trajectory launches to the West but in each case the projectile cleared the lawns and main house before being lost in the distance and the valley below...

[Ray P]

so given that sequence of posts why would he 'arguably' specify only the time it took to come down?

Ed, there are two Nicks in the conversation,Nick and Jack(aka Nick). I was referring to Jack's words which can be read as saying he only timed the descent. I actually appreciated that it was the imprecision of the language and it was almost certainly a 7sec round trip but sometimes it can be a little fun to be pedantic - don't take it to seriously.

I'm with you though on whether it is likely to be 3.5sec up and 3.5sec down as the initial acceleration at launch may well be greater than the acceleration on the way down, and with a faster object drag will have a greater influence. It's not just drag though, any wind will modify the trajectory too.

Anyway, the whole cannon thing sounds like a heap of fun.

[ed]

don't take it to seriously.

snigger