Velocity

[acesonly532]

i learned all about this in school for a year. we would do all problems about baseball. this is hard to explain but when a ball is hit in a baseball, is the parabola perfectely symetrical. Is there an equal distance from the peak to where it was hit to where it landed. I thought and still do, that, when a baseball is hit it rises slowly comes to a peak, and falls at a much greater rate than when it rises


i drew a picture but don't know how to put it on here.

[-zero-]

...are you in highschool? projectile motion is pretty standard.

[jman220]

[ QUOTE ]
i learned all about this in school for a year. we would do all problems about baseball. this is hard to explain but when a ball is hit in a baseball, is the parabola perfectely symetrical. Is there an equal distance from the peak to where it was hit to where it landed. I thought and still do, that, when a baseball is hit it rises slowly comes to a peak, and falls at a much greater rate than when it rises


i drew a picture but don't know how to put it on here.

[/ QUOTE ]

In a vaccuum it would be a perfectly symmetrical parabola. However, air friction prevents this.

Edit: Same principle applies to objects goiing up and coming back down, if there was no air friction, and you shot a bullet straight up into the air, at the moment before it hit the ground (on the downswing) it would have the same velocity as when it was fired from the gun.

[acesonly532]

then can you explain it...

so this isnt true becaus everytime i see a ball hit it looks like the distanse between its peak and ending point distance is much greater than its distance between peak and starting point distance. my teacher at the time said that the distance to the peak from the start and ending points is always the same creating a perfect, symmetrical line=parabola

[jman220]

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everytime i see a ball hit it looks like the distanse between its peak and ending point distance is much greater than its distance between peak and starting point distance.

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I think your'e trying to say the opposite and you've switched it up? When a baseball is it, as it ascends, air friction is acting to decelerate its forward momentum, thus when it reaches its pinnacle, it is travelling slower than then when it was hit, so as it descends, its forward momentum relative to the ground is a lto less, and the arc is much smaller. This produces the effect that when a baseball is hit, it goes forward farther as it goes up than when it comes down (which is also an observable phenomenon, and the exact opposite of what you have said).

[acesonly532]

your right...i mixed up my words that is exactly what i meant...

[jman220]

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your right...i mixed up my words that is exactly what i meant...

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Well then your teacher is right when speaking in terms of a vaccuum, but it doesn't work in the real world where there's air friction. Its the same reason why a bowling ball does in fact fall faster than a feather, in a vaccuum they wouldn't, but int he real world, we have air. Here's a badly drawn picture:

http://img154.imageshack.us/img154/3962/baseball1ba.jpg

[jman220]

However, you are wrong when you say that a baseball "falls at a much greater rate than when it goes up." If anything, although not really noticeable, the baseball will fall at a slower rate (again due to air friction) than the way in which it ascended.

[acesonly532]

i was refering to slope

[Copernicus]

[ QUOTE ]
i was refering to slope

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Your picture taking into account air friction assumes no backspin on the ball...ie no spin, or overspin. If there is backspin it could look more like frictionless, or even reverse the slope of "with friction". Or, more noticeable with a golf ball with back spin, there might be two very different slopes during ascent...shallow and then steep.

[Borodog]

I whipped this up:

http://i27.photobucket.com/albums/c153/Borodog/Trajectory.png

This is the trajectory of a 1kg projectile fired from the origin at an angle of 45 degrees above the horizontal, with an initial speed of about 42.4 m/s, and a drag coefficient of 0.3kg/s. The units on the axes are meters.

I can show you the equations of the solution if you're interested; it's not particularly pretty.

[Borodog]

Just because every child should know:

http://i27.photobucket.com/albums/c153/Borodog/equation.gif