Robittybob1 Posted May 7, 2015 Posted May 7, 2015 At the local playground on the "Merry go round" if you mounted a gun that would fire bullets radially outward and mounted a target to the whole system. Do you think the bullets will hit the target if the turntable was rotated rapidly? Kids stand back!
imatfaal Posted May 7, 2015 Posted May 7, 2015 At the local playground on the "Merry go round" if you mounted a gun that would fire bullets radially outward and mounted a target to the whole system. Do you think the bullets will hit the target if the turntable was rotated rapidly? Kids stand back! Depends where you put the target.
studiot Posted May 7, 2015 Posted May 7, 2015 and mounted a target to the whole system. Depends where you put the target. Immediately behind the gun of course, since it is well known that immediately in front of the gun is the safest place on the firing range.
swansont Posted May 7, 2015 Posted May 7, 2015 Depends also on what a target "mounted to the whole system" means. Assuming you mean a target across from you on the rotating platform, at some reasonable distance: People would have a tough time hitting, especially if not given an opportunity for feedback with multiple shots. But you could calculate the deviation with sufficient information, so if there was some sort of mechanical mount to allow for such aiming, you could hit it quite readily. Not really seeing how this leads into a discussion on radial vs tangential motion, or angular momentum.
xyzt Posted May 8, 2015 Posted May 8, 2015 At the local playground on the "Merry go round" if you mounted a gun that would fire bullets radially outward and mounted a target to the whole system. Do you think the bullets will hit the target if the turntable was rotated rapidly? Kids stand back! Imagine that you want to shoot something that is placed diametrically opposed to you. Should you aim straight down the diameter? You can analyze the problem from either the perspective of the inertial frame of the ground or from the POV of the non-inertial rotating platform. The answer will be the same: 1. From the ground frame POV, if you aim straight down the diameter , you will miss. The reason is that while the bullet travels down the straight line of the diameter, the target moves, so you'll miss. It is an aberration effect. 2. From the POV of the platform things are a little more complicated. The bullet is subjected to the fictitious Coriolis force, so its trajectory will be "bent" and will not follow the diameter drawn on the platform. So, you'll miss. Not a bad question....
Robittybob1 Posted May 8, 2015 Author Posted May 8, 2015 (edited) Depends where you put the target. I should have made it clear that while the merry go round (mgr) was stationary I had no problems in getting a bullseye on the target. It is on a very long extension horizontally out from the mgr. so the target rotates at the same rate as the mgr. Immediately behind the gun of course, since it is well known that immediately in front of the gun is the safest place on the firing range. I'm not going to go hunting with you. Depends also on what a target "mounted to the whole system" means. Assuming you mean a target across from you on the rotating platform, at some reasonable distance: People would have a tough time hitting, especially if not given an opportunity for feedback with multiple shots. But you could calculate the deviation with sufficient information, so if there was some sort of mechanical mount to allow for such aiming, you could hit it quite readily. Not really seeing how this leads into a discussion on radial vs tangential motion, or angular momentum. So I think you were describing a mounted gun firing at a ground based target. Well I wasn't trying to describe it like that, but more like that "radially outward" diagram you drew on the other thread. http://www.scienceforums.net/topic/88420-centrifugal-forces-appear-to-act-opposite-to-gravity-how-is-this-possible/page-12#entry866619 Imagine that you want to shoot something that is placed diametrically opposed to you. Should you aim straight down the diameter? You can analyze the problem from either the perspective of the inertial frame of the ground or from the POV of the non-inertial rotating platform. The answer will be the same: 1. From the ground frame POV, if you aim straight down the diameter , you will miss. The reason is that while the bullet travels down the straight line of the diameter, the target moves, so you'll miss. It is an aberration effect. 2. From the POV of the platform things are a little more complicated. The bullet is subjected to the fictitious Coriolis force, so its trajectory will be "bent" and will not follow the diameter drawn on the platform. So, you'll miss. Not a bad question.... Very clever, so you mounted the target on the opposite side of the mgr and it still misses the target! If the bullet is fired outward into the playground The Mythbuster team showed the bullet from a rotating gun follows a straight path. But it can't leave the barrel at an angle, but it must take on the tangential motion of the gun. So it is not radially out and not tangential either. Can you explain it better please? http://www.discovery.com/tv-shows/mythbusters/videos/curve-a-bullet-minimyth/ Edited May 8, 2015 by Robittybob1
swansont Posted May 8, 2015 Posted May 8, 2015 I should have made it clear that while the merry go round (mgr) was stationary I had no problems in getting a bullseye on the target. It is on a very long extension horizontally out from the mgr. so the target rotates at the same rate as the mgr. The problem you described in the OP has it rotating rapidly. If it's stationary, there is no connection to radial vs tangential motion, or angular momentum.
Robittybob1 Posted May 8, 2015 Author Posted May 8, 2015 The problem you described in the OP has it rotating rapidly. If it's stationary, there is no connection to radial vs tangential motion, or angular momentum. OK, the point is while it was stationary there was no problem but when you rotate the turntable rapidly, will the target still be easy to hit?
Strange Posted May 8, 2015 Posted May 8, 2015 OK, the point is while it was stationary there was no problem but when you rotate the turntable rapidly, will the target still be easy to hit? Didn't xyzt's post answer this in sufficient detail?
Robittybob1 Posted May 8, 2015 Author Posted May 8, 2015 (edited) That was great thanks. Would that be described as throwing the ball radially inward from a rotating platform? The ball goes along a radius when it is not rotating, but when the turntable is rotating can you still see the effects of the tangential velocity? PS: Looking at it again, when viewing the ball from the camera back to the thrower (1:30 onward) you see the ball moving sideways with respect to the background. Didn't xyzt's post answer this in sufficient detail? I couldn't see that he has accounted for the tangential velocity from the ground frame POV. Edited May 8, 2015 by Robittybob1
swansont Posted May 8, 2015 Posted May 8, 2015 I couldn't see that he has accounted for the tangential velocity from the ground frame POV. "the target moves"
xyzt Posted May 8, 2015 Posted May 8, 2015 (edited) "the target moves" Sigh.... Didn't xyzt's post answer this in sufficient detail? Sigh..... Edited May 8, 2015 by xyzt
Robittybob1 Posted May 8, 2015 Author Posted May 8, 2015 "the target moves" If "the target moves" the gun moves too doesn't it?
xyzt Posted May 8, 2015 Posted May 8, 2015 (edited) If "the target moves" the gun moves too doesn't it? They move in OPPOSITE directions. This DOUBLES the effect. Have you watched the video? Did you bother to read the wiki article on the Coriolis effect? Sigh. Edited May 8, 2015 by xyzt
Strange Posted May 8, 2015 Posted May 8, 2015 Have you watched the video? It even has great big unmissable dotted lines showing the path of the ball in both frames of reference. But I guess Rob missed those.
Robittybob1 Posted May 8, 2015 Author Posted May 8, 2015 They move in OPPOSITE directions. This DOUBLES the effect. Have you watched the video? Did you bother to read the wiki article on the Coriolis effect? Sigh. Not since I've started the thread, no. Does it mention about doubling the effect does it? I'll have another look. It even has great big unmissable dotted lines showing the path of the ball in both frames of reference. But I guess Rob missed those. Once the ball is released no more forces act on it so as we established it must travel in a straight line, the dotted lines didn't show the path of the ball while it was held and as it was being accelerated during a throw and only straight after it is released.
xyzt Posted May 8, 2015 Posted May 8, 2015 Not since I've started the thread, no. Does it mention about doubling the effect does it? I'll have another look. Yes, it does. You need to follow the math.
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