just throwin this out there

GrimJack

Administrator
Dec 31, 1969
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americanjebus, what answer did you turn in? And let us know whether you get it right or wrong. :) I'm betting I'm right.

Let's hit this from a different angle.

Do you think that you can have acceleration when you are already at 100mph? SO for instance, if you accelerate from 0 to 200 mph, do you think that you are accelerating when you hit 100mph?

The only difference is the start and stop speeds... and as acceleration is a change in velocity, the start and stop speeds are irrelevant.

In other words, the only time that your acceleration is zero, is when your velocity is constant. If you are changing speeds, whether it's from 0 to 200, -100 to 100, or 0 to -200, your are always under acceleration.
 
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lanky189

Guest
alot of people get confused with the false concept (when dealing with conceptual physics) of de-celeration. There really is no such thing. Acceleration just what grim says..a CHANG in velocity.. velocity is speed and direction..so change direction and guess what..you've changed acceleration. Slow down..and your accelerating...speed up and your accelerating..its all the same thing..
 

turbo

Mr. Clean
Apr 27, 2005
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The coordinate system you choose sets up the sign of acceleration and direction of the velocity relative to the displacement. The answer is yes because the acceleration is still changing even though the velocity is zero. A ball in the air can have zero velocity but a negative acceleration.
 

GrimJack

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Dec 31, 1969
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Ball in the air - damn fine analogy. Thanks for the idea!

OK... here we go.

Gravity accelerates EVERYTHING on the planet that isn't on the ground at a specific rate, 9.8m/s^2 - and it does this all the time.

So... throw a ball straight up. When it hits the top of it's path, it's velocity = zero. However, it's still accelerating, as gravity is a constant, thus, it will fall back to earth.
 

SupraMario

I think it was the google
Mar 30, 2005
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Well, i have come to the conclusion that i was wrong, i had something else in mind and after re-reading grims post i know understand the concept.
Grim-1 / Me-0
 

americanjebus

Mr. Evergreen
Mar 30, 2005
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GrimJack said:
Ball in the air - damn fine analogy. Thanks for the idea!

OK... here we go.

Gravity accelerates EVERYTHING on the planet that isn't on the ground at a specific rate, 9.8m/s^2 - and it does this all the time.

So... throw a ball straight up. When it hits the top of it's path, it's velocity = zero. However, it's still accelerating, as gravity is a constant, thus, it will fall back to earth.


yea too bad i got that answer to late. i wrote no, but the afternoon after turning it in i realized. OH shit i can happen cus i had never thought of an expample, then ithought of the ball.

my teacher used the same exampl. constant accel of 9.8m/s acting on all objects at all times but when the ball stalls the velocity is zero but teh accell will ALWAYs be 9.8m/s due to gravity.

i wrote no so i got it wrong but atleast i know the real answer now. meh 9.5/10 isnt a bad score i geuss.
 

Tigerkat229

Sexy Kitty
Aug 2, 2005
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GrimJack said:
Ball in the air - damn fine analogy. Thanks for the idea!

OK... here we go.

Gravity accelerates EVERYTHING on the planet that isn't on the ground at a specific rate, 9.8m/s^2 - and it does this all the time.

So... throw a ball straight up. When it hits the top of it's path, it's velocity = zero. However, it's still accelerating, as gravity is a constant, thus, it will fall back to earth.

Shit...

All those physics classes and i still fuck this up...

Ok i was wrong, way to go Grim :)
 

americanjebus

Mr. Evergreen
Mar 30, 2005
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what do you mean.

the 9.8m/s is the acceleration due to gravity, every second after you drop something its rate of fall increases by 9.8 meters every second. the 9.8 IS the acceleration but only in terms of gravitational acceleration

its wrong to call it gravity, cus gravity itself is something else.
 

Squid699

Manic Mechanic
Mar 30, 2005
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The sea-level gravitational acceleration is 9.780 m/s², not just 9.8m/s. This is constant accelleration until the object reaches terminal velocity, where atmospheric drag cancels out further accelleration and then falls at a constant speed.
 
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lanky189

Guest
Terminal Velocity, also a quasi-enjoyable film staring Charlie Sheen
 

Shawndude

New Member
Mar 30, 2005
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It's all relative.

As Grim points out, acceleration references itself, not some outside measurement or reference. Just because you're standing still relative to something that usually doesn't move, doesn't mean you're not accelerating.
 

supra90turbo

shaeff is FTMFW!
Mar 30, 2005
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we are all technically accelerating, even when standing still. the earth is moving, hence our bodies are in motion relative to a point in space.
 
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lanky189

Guest
Shawndude said:
It's all relative.

As Grim points out, acceleration references itself, not some outside measurement or reference. Just because you're standing still relative to something that usually doesn't move, doesn't mean you're not accelerating.



So you're not dead eh? :wavey:


what the hell is goin on shawn..havent heard from you in a long time.