A physics puzzle

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Claude
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A physics puzzle

Post by Claude »

The scene: A truck, carrying a canon, pointing out the back, loaded with a soccer ball.

The speed of the soccer ball shot from the canon is 50Mph.

As the canon is being shot, the truck travels at 50Mph.

Question: What happens to the Ball ?

(Please use the spoiler tag for your answers!)
Cheers, Claude.

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StuartR
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Re: A physics puzzle

Post by StuartR »

I assume that
Spoiler
The ball travels away from the truck at 50MPH, remaining stationary relative to the ground. BUT this would just be for the split second after the cannon fires
StuartR


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AlanMiller
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Re: A physics puzzle

Post by AlanMiller »

Spoiler
It could end up travelling at 100 mph, if the truck was travelling in reverse at the time!
Alan

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HansV
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Re: A physics puzzle

Post by HansV »

Spoiler
The cannon ball will fall straight down (more or less) - see If You Are Moving at the Speed of a Bullet and Shoot Backwards, What Happens? for a video that demonstrates this.
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Rudi
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Re: A physics puzzle

Post by Rudi »

Spoiler
That was my "logical" guess; but thanks for the video proof Hans (and Mythbusters!)
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Rudi

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ChrisGreaves
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Re: A physics puzzle

Post by ChrisGreaves »

HansV wrote:
Spoiler
The cannon ball will fall straight down (more or less) - see If You Are Moving at the Speed of a Bullet and Shoot Backwards, What Happens? for a video that demonstrates this.
Spoiler
But not if the cannon-ball was composed of photons!
Which would obviate the question posed by our correspondent in "reversed"
Cheers
Chris
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HansV
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Re: A physics puzzle

Post by HansV »

A soccer ball composed of photons?
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Hans

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Claude
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Re: A physics puzzle

Post by Claude »

ChrisGreaves wrote:But not if the cannon-ball was composed of photons!
I think you've been PhotonShopping too much :smile:
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ChrisGreaves
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Re: A physics puzzle

Post by ChrisGreaves »

HansV wrote:A soccer ball composed of photons?
Funny you should mention that ....

Many tears[sic] ago I read a book on Physics in which the author likened a search for particles as being rather like watching a soccer game in which the ball was invisible.

Of course, the players appear to be wandering around the field aimlessly for twenty minutes, occasionally falling to the ground and clutching a knee, shin, foot, or head.

Mystified, our observer finally notices that just before half the players raise their arms and cheer, a bulge appears for a second or two in the back of the net ...

Speaking of which:
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Chris
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ChrisGreaves
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Re: A physics puzzle

Post by ChrisGreaves »

Claude wrote:I think you've been PhotonShopping too much :smile:
Claude, you are, as usual, absolutely correct.
Just yesterday I came across this in a book:-
IMG_20180201_093452774.jpg
The little essay is the one about tea leaves, why they congregate in the centre of the base of a mug.
The book:-
IMG_20180201_093523188.jpg
Cheers and Swerves
Chris
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Claude
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Re: A physics puzzle

Post by Claude »

StuartR wrote:BUT this would just be for the split second after the cannon fires[
No need for that part of your statement Stuart. :smile:

Anyway, I just thought I'd use a 'puzzle' to bring this (un)expected fact to attention of loungers.
Cheers, Claude.

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AlanMiller
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Re: A physics puzzle

Post by AlanMiller »

Closely related to the aspect of this I presume you were trying to point out Claude, is the Bullet Fired vs Bullet Dropped demonstration.

Alan

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AlanMiller
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Re: A physics puzzle

Post by AlanMiller »

HansV wrote:A soccer ball composed of photons?
Neutrinos would work too ... and be just as likely as a soccer ball made of photons!

Alan

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StuartR
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Re: A physics puzzle

Post by StuartR »

Claude wrote:
StuartR wrote:BUT this would just be for the split second after the cannon fires[
No need for that part of your statement Stuart. :smile:
I didn't want to discuss the issues of continued acceleration from the expanding air still leaving the cannon, and wind resistance.
StuartR


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AlanMiller
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Re: A physics puzzle

Post by AlanMiller »

StuartR wrote:I didn't want to discuss the issues of continued acceleration from the expanding air still leaving the cannon, and wind resistance.
Wise decision too!
Transitional ballistics is the least well understood of the ballistic regimes, but the best for sales of headache tablets to those unfortunate enough to have to work in it. :sad:

Edit: But on that topic, I just stumbled on the best video I've seen of the phenomena involved - even captures the "shock diamonds" in the aftermath.

Alan