If A Cannonbal Was Fired Verticaly From A Moving Train

[jolly geoff]

where would it land ,behind,infront or on the train

[Prudie]

Depends on:
How fast the train is travelling
Which part of the train it was fired from
The mass of the cannonball and force that it was fired with

I don't see how it could ever land in front of the train unless it went up at angle

[fiction-factory]

If the train was moving at 50 mph (say) the cannon ball would be moving at the same speed when it is fired.
Are we assuming no air resistance or wind factors?

[ToraToraTora]

assuming this is the well known thought experiment about relative motion and we thus ignore the air it would go back in the cannon.

[fiction-factory]

Should land on the train if the train speed is constant all things being equal

[fiction-factory]

https://www.wired.com/2017/04/wacky-physics-firing-ball-moving-cart/
see demo here

[Prudie]

Why? If it goes up vertically why should it land on the train. If you pointed a gun skyward from a moving train it's highly unlikely the bullet would land back on a the train.

[fiction-factory]

Because all the matters is what happens in the horizontal direction. The cannon ball starts at the same speed as the moving train and aparrt from air resistance (which is usually ignored in these questions) there is no change in velocity in the horizontal direction

[zebo]

If it was fired from the rear of the train then it would surely land behind of it was fired hard enough, in the time it was in the air the train would have moved forward. In order to fly vertically from a moving train, at what angle would it need to be fired to overcome the initial influence of the train's velocity? Resolution of forces maybe?
We once had a visit to a float glass factory in St Helens, where else, and we watched a nonstop belt carrying float glass being cut. The calculation of the angle of the cut to ensure a cut perpendicular to the side was fascinating.

[ToraToraTora]

think it through prudie!

[fiction-factory]

But the cannon ball is moving forwards at the same speed as the train. It depends on whether you assume that air resistance would slow it down sufficiently. In reality it would if teh missile was in the air long enough, but we need to know the assumptions. If it was a physics question you would/should be told the assumptions

[ToraToraTora]

no, zebo, see FF's link

[ToraToraTora]

ok how about if you are standing in a train carriage moving at 100mph and you jump in the air, do you land behind where you took off? of course not.

[fiction-factory]

First, do we agree or disagree that if we jump up in the air on a train/plane we land where we started not several feet behind the train?

[fiction-factory]

Ha, sorry TTT. Fools seldom differ and all that

[Prudie]

No of course not but you are not jumping with the force of a cannon fire and even more so a gun shot.

[jolly geoff]

fiction factory seems to have seen the same demo as i have , which has the cannon ball landing back in the cannon but i believe the demo is floored as it doesnt take account of air friction which would slow the cannonball down ,just wondered if others agreed with me that it would land behind the train

[ToraToraTora]

I give up!

[fiction-factory]

If the train is travellinat 60mph that's 27m/s, so even if you were in the air for half a second would you land 13.5 m back?

[johnny.5]

is it an electric train or steam train or diesel train ??

[fiction-factory]

This sort of thing was covered quite a bit in the first parts of Mechanics in Maths or Physics A level (although the cannons were usually fired at angles).We solved them by separating the horizontal and vertical aspects. Here we only need to consider the horizontal factors. The key is whether the air resistance is enough to make a significant difference.