Phi for All Posted August 24, 2004 Posted August 24, 2004 At first it seems counter-intuitive' date=' but it's not really. Each acceleration is independent. Thus, if you drop a bullet from the height of the barrel at the same instant you fire the gun, both bullets will still hit the ground simultaneously. (this is assuming the bullet produces no lift). A better example is to roll a moving ball off a ledge while simultaneously dropping another ball from the same height. I'm inclined to say the puppy would bounce [/quote']First off, YAY! Finally someone agrees with me on the puppy bounce! Next, suppose you simultaneously drop a bullet straight down, fire a .30 caliber bullet with 125 grains of gunpowder from one gun, and also fire a .30 caliber bullet with 220 grains from another gun, assume no lift from either fired bullet, no wind, etc. They're all going to hit the ground at the same time?
jordan Posted August 24, 2004 Posted August 24, 2004 No. The bullet fired straight down will hit first because you have added verticle energy to the system through the powder. The other ones that fire verticly do not have energy transfered to verticle motion. All the energy of the explosion goes to horizontal momentum. Therefore, when energy is in equal quantities for the verticle axis, the bullet will reach the destination at the same time. This is true for the horizontal axis too, but that would require a different example. 1) Bullet fired from gun and bullet dropped from same hight as gun: Both hit the ground at the same time because both rely entirely on gravity for verticle acceleration. Neither has any added energy in that direction. 2) Bullet fired from gun tilted slightly at the ground and bullet dropped from same hight as gun: The fired bullet will hit the ground first because it has some energy in the verticle axis. Though most of the energy is going horizontal, some is still giving it a push towards the ground. The exact forces the push verticle and horizontal invovle sine and cosine stuff to calculate.
blike Posted August 24, 2004 Posted August 24, 2004 No. The bullet fired straight down will hit first because you have added verticle energy to the system through the powder. He said "drop one straight down". Phi, if the guns fired perfectly horizontal and simultaneously, they will all hit the ground at the same time. The one with more charge will have faster horizontal motion, but the vertical motion of all the bullets is dictated by gravity alone [as long as the guns are fired horizontally]. See jordan's post for more details
Phi for All Posted August 24, 2004 Posted August 24, 2004 The only bullet going straight down is dropped. The other two are fired vertically.
blike Posted August 24, 2004 Posted August 24, 2004 If the gun is vertically it's a different story, because you've added acceleration other than gravity to the system.
Phi for All Posted August 24, 2004 Posted August 24, 2004 No, I misstated that. Bullet A dropped, bullets B & C fired horizontally with differing powder charges. I see what you're saying, the extra powder will make bullet C go farther than B, but they'll hit the ground simultaneously. It does seem counter to logic, but damn it, blike/Gallileo, YOU'RE RIGHT! What if the tower you did this from were leaning....
Cap'n Refsmmat Posted August 24, 2004 Posted August 24, 2004 http://solomon.physics.sc.edu/~tedeschi/demo/demo3.html Read it all, try the movie.
Phi for All Posted August 24, 2004 Posted August 24, 2004 This might be more useful:Too funny. If we could just get the oddfreak to climb to the top of a 30' tower.
jordan Posted August 24, 2004 Posted August 24, 2004 I got 1550 points. Horray. And the puppy splatted, not bounced. Problem solved.
Dave Posted August 24, 2004 Posted August 24, 2004 I always said there should be a coefficient of splatterness in mechanics
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