Imagine throwing a baseball straight up into the air as hard as you can, or a gun shooting straight up.. whatever...

At the moment the the object leaves your hand, does it:

1. continue accelerating, then start decelerating due to gravity.

2. instantly start decelerating.

3. continue at the speed it left your hand for a short bit and then start decelerating..

or am I way off base here.. This was just something I was thinking about the other day..

i took quite a few physics classes, and i think i remember how we wrote up the numbers for the forumulas.

take the distance from the part of your hand to last touch the baseball, to the point where the baseball stops going up. the force of gravity is 9.8m/s so that entire distance would be affected by it. so as soon as your hand stops touching it it starts to deccelerate because there isn no more force on the ball making it go up.

the only way in physics you have a constant acceleration without a change in speed, is when the direction is constanly changing. like a car doing dougnuts, or a car placed on a record player. do not try to argue this, my phyisics teachers yelled and repeated it untill everyone learned it. and it was in the book

quote constant acceleration without a change in speed

Ummmm, what?

its true, because direction changes everything. i dont know why, that just the way it is. look it up.

quote the only way in physics you have a constant acceleration without a change in speed, is when the direction is constanly changing.

This is true.

average Acceleration = a change in velocity of an object during a time period divided by the length of that time period.

average Velocity = a change in position during a time period divided by the length of the time period.

So if you are driving around a rotary at a constant 25 MPH, you are constantly accelerating, going by the currently accepted definition of acceleration.

[This message has been edited by Tweek (edited 07-04-2001).]

WOOHOO

feels good to retain information

im going to blow doughnuts in the parking lot to excersize this when i get home

[This message has been edited by mrgone (edited 07-04-2001).]

Yep #2

At the exact point you let go of the ball it has maximum kinetic energy. As the ball decelerates it is gaining potential energy until it reaches it's maximum PE at the maximum height.

All deals with the conservation of energy equation where energy cannot be created nor destroyed.

E=(sum of all KE)-(sum of all PE) or something like that

So, was the correct answer A, B or C?

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'Consciousness: That annoying time between naps.'

MM

Only monkeyman would ask if the correct answer was A B or C , if the options were 1 2 or 3 ( starts decelerating instantly)

Since I used to teach high school physics full time...I suppose I'm qualified to answer this one

The answer is really none of the above. Technically the correct answer would be that the baseball (or whatever) would begin accelerating at a rate of approximately -9.8 m/s^2 at the moment the ball leaves the hand and is primarily under the influence of gravity (we'll ignore things like air resistance and so on to simplify things).

In common language, when things speed up, we say that they are "accelerating", and, when they slow down, we say that they are "decelerating". However, in the language of physics, we say that both objects are accelerating, not because both objects are speeding up, but because both objects have changing velocities. We only deal with positive acceleration (increasing velocity) and negative acceleration (decreasing velocity). Gotta have positive and negative values otherwise all those cool formulas won't work right.

Oh yeah, mrgone you hit the nail on the head why an object might be accelerating even though its speed is constant. You get an "A" for the day Since acceleration involves a change in velocity, an object might be accelerating even though its speed is constant. Why is this possible? Well, it goes back to the difference between speed and velocity. Remember that velocity involves both speed and direction. So, a changing velocity does not have to necessarily involve a change in speed. It could just involve a change in direction, just like Tweek's example of driving around in a circle at a constant speed.

Class dismissed....

Ken S.

[This message has been edited by kslish (edited 07-04-2001).]

Is the final going to be multiple choice or essay? Any bonus points?

And will we need or can we use a calculator to like figure this out if need be?

I've never been good at tests. Ask my wife. She'll tell you I'm still studying for the pregnancy test!

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quote Originally posted by Phil: Only Monkeyman would ask if the correct answer was A B or C , if the options were 1 2 or 3 ( starts decelerating instantly)

Ummm...Thank you? At least I'm able to live up to my reputation (whatever that is).

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'Consciousness: That annoying time between naps.'

MM

Boy, I got all excited when I saw this thread involving physics! Then I saw the question had been answered in its entirety...

Physics has been my favorite class so far, and I plan on taking AP Physics next year (senior year in HS, yes I'm young!)

Our exam this year was at Cedar Point, like finding the g forces, KE/PE, rotational velocity/inertia, and all that good stuff of the rides.

We snuck a g-force meter thingy on to the new Millenium Force (they'll yell at you if you dont have everything secured), and at the bottom of the first hill there were 3.2 g's!!

Question, if a pine tree air freshener falls in the woods and makes you drop your donut (and thus breaking it..) while you're tossing this ball up in the air, is Galen still a goof?

(just kidding galen. hehe)

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steve@fieroproject.com
http://www.fieroproject.com

Can we move on to History or Politics?
My brain begins to hurt after basic Algebra.

Ok...so if I launched my Fiero off a 4 foot high 34 degree angled ramp at 80 miles an hour. How close would my other ramp need to be to not trash my Fiero on landing?

Just thought you physics types could save me a guesstimate and possible misshap..lol

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My Fiero
Need a Subwoofer Console or Speaker Door Pods?

Aus--You might want to try that 1st with your new donor car.

quote Originally posted by AusFiero: Ok...so if I launched my Fiero off a 4 foot high 34 degree angled ramp at 80 miles an hour. How close would my other ramp need to be to not trash my Fiero on landing? Just thought you physics types could save me a guesstimate and possible misshap..lol

LOL!
Welp we have a few more variables to consider
1 The last psycheatric evaluation you had
2 The location of your Fiero prior to this
3 How will you do it without your fiero since I will have it.
4 How you will recover your car once you decide not to do it
5 The realivence and usefullness of this thread as a whole

quote Originally posted by AusFiero: Ok...so if I launched my Fiero off a 4 foot high 34 degree angled ramp at 80 miles an hour. How close would my other ramp need to be to not trash my Fiero on landing?

Assuming the other ramp is also 4' high, you'd need 388 feet between ramps. Since the center of pressure for a Fiero is ahead of the center of mass, you'll want to install a reverse spoiler to keep the back end from sinking and striking the ramp first.

Note: thanks for making the ramp a 3-4-5 right triangle, makes the math much easier.

heres a toughy...if your in a jet going at 500mph and eject (at a rate of 3Gs) what is your bodys speed after you clear the aircraft? a/ 500 mph... b/1500 mph....c/other

Or more importantly, what's your bodys speed when it hits the ground?

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'Consciousness: That annoying time between naps.'

MM

Two trains. One train leaves from New York at 3:45p.m. Heading to New Jersey. The other train leaves Chicago at 2:15p.m. Heading to New York. How much change do you have in your pocket?

quote Originally posted by rogergarrison: heres a toughy...if your in a jet going at 500mph and eject (at a rate of 3Gs) what is your bodys speed after you clear the aircraft? a/ 500 mph... b/1500 mph....c/other

c/ need more information.

If the plane is going 500mph, you are too.

Just like if you are on a passenger plane, and throw a ball up, it does not coming flying back at hit you in the face, from the plane "moving out from underneath it" or something like that. All motion is relative; if the ball is sitting in your lap, there is no motion between you and the ball, but both you and the ball and everything else on the plane are going x mph.

So, if you are going 500mph in a jet, and eject, you will continue to go 500mph until air resistance and gravity take over (rather quickly)

Even though you have a simulated weight of 3g's, the plane does too, and everything else in the plane. When you eject, and are still going 500mph, you'll still be pulling 3g's, until you start to accelerate until you hit terminal velocity while you are falling.

Well, I think that's right. I may have missed something major here. I dont know how correct it is, but it seems pretty good. I do know that I am tired, so goodnight all!

quote Originally posted by FieroJoe: I may have missed something major here.

I think you did. I believe that the 3G acceleration was on you by the ejector seat, not on the plane. Therefore, you may or may not be traveling at 500 mph anymore, depending of the vector of the ejection charge compared to the vector of the aircraft's velocity. Also, does your velocity depend on if you are wearing your seatbelt?

Note: 3Gs is low for an ejection seat.

i was just curious, picked some hypothetical numbers. most ejection seats fire you up usually at almost a 90* angle from aircraft path. Although true you are going 500 mph forward, you arre also accelerating upward. making your flight path the hypotenuse (spl?) of a triangle. I would therefore believe you would have to be traveling faster at some point than the aircraft. Seems to me from flight school there was some formula to figure this out. (btw if your chute works like it should, you should land on the ground at a speed less than 5 or 10 mph)

....to answer Steven Wright's question:
if you had a car that traveled at thee speed of light, and you turned on the headlights, would they do anything?

...n'yuk, n'yuk, n'yuk

that's something to think about.
check this math out
3 men pay equally on a motel room. the room is 30.00 total so they pay 10.00 apiece.
the manger realizing that on monday night the room was only 25.00 sends the bellhop
up to give them a 5.00 discount. he decides
on the way up 5.00 cant be divided equal between the three men,so he puts 2.00 in his pocket and gives them back a buck.
now they paid 9.00 apiece instead of 10.00 so 3 x 9=27 + 2.00(in the bellhops pocket) is 29.00 one dollar is missing!

quote Originally posted by Steve Normington: I think you did. I believe that the 3G acceleration was on you by the ejector seat, not on the plane. Therefore, you may or may not be traveling at 500 mph anymore, depending of the vector of the ejection charge compared to the vector of the aircraft's velocity. Also, does your velocity depend on if you are wearing your seatbelt? Note: 3Gs is low for an ejection seat.

Yeah, no kidding. A typical ejection is between 15 and 20 G's, depending on the weight of the ejectee.

15 and 20 G's!!! Holy Sh*t! So, whats the percentage of people that pass out? Do the chutes automatically deploy? I would hope so incase you passed out. I thought that after about 10 G's things in your brain start shutting down if you can't hold enough blood up there.

quote Originally posted by TI_3VOM: ....to answer Steven Wright's question: if you had a car that traveled at thee speed of light, and you turned on the headlights, would they do anything? ...n'yuk, n'yuk, n'yuk

Unless you didn't have an alternator, the load on the motor the alternator causes to charge the battery back up would slow the car down to at least just before the speed of light.

Seems like it'd as good of an answer as any.

[This message has been edited by Pontiaddict (edited 07-07-2001).]

ok, heres a few theories that I heard in astronomy class, stick em together (in my fairly creative way) and the results are quite worrying, if I remember this right
Theory 1: Time slows down as you speed up
Theory 2: Objects approaching the speed of light increase in mass until they have infinite mass at the speed of light.
Theory 3: An object in motion will stay in motion unless acted upon by an outside force.
Now, Speed is determined by distance over time, and if time slows down at high speeds, it must slow down imperceptibly at lower speeds. If you are covering the same amount of distance, but time has slowed, you are covering More distance in the original about of time, thereby accelerating.
Out in deep space, where theres no gravity (even from nearby stars, too far away) a moving object must be speeding up as its relative time slows down, if this goes on long enough, it will hit the speed of light, thereby attaining infinite mass, And Infinite Gravity, which would pull everything in on it , which at infinite gravity would collapse the universe. Why hasn't this happened yet?

quote Originally posted by Rex: that's something to think about. check this math out 3 men pay equally on a motel room. the room is 30.00 total so they pay 10.00 apiece. the manger realizing that on monday night the room was only 25.00 sends the bellhop up to give them a 5.00 discount. he decides on the way up 5.00 cant be divided equal between the three men,so he puts 2.00 in his pocket and gives them back a buck. now they paid 9.00 apiece instead of 10.00 so 3 x 9=27 + 2.00(in the bellhops pocket) is 29.00 one dollar is missing!

<cracks his knuckles and breaks out the accounting book>

From your assertations, lets see if I can find the buck...you can make alot of phone calls on a buck they say!

3 People
$30 for the room
$5 refund
$2 Pocketed
$3 Actually returned.

$30/3 = $10 per person

After refund of $5.00 and knowing the total cost of the room now was at $25.00 for 3 people.

Therefore, $30 (orig)-$5 (refund or "Returns and Allowances") = $25 (Actual room price). $25/3 = $8.33333... (w/3 repeating therefore $8.33 rounded) per person.

$3/3 = $1.00 per person refund.

$8.33+$1.00 = $9.33 (keep in mind rounding) actually paid per person

$9.3333333...*3 = $28.00

$28.00 + $2.00 pocketed = $30.00

Whew!

So much for making a phone call with a buck like they advertise!

BTW, from a previous post of mine in a thread here in O/T, has anyone figured out the mathimatical formula for a "SNIFFLE" from the problem I gave?

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[This message has been edited by JSocha (edited 07-07-2001).]

quote Originally posted by JSocha: <cracks his knuckles and breaks out the accounting book> From your assertations, lets see if I can find the buck...you can make alot of phone calls on a buck they say! 3 People $30 for the room $5 refund $2 Pocketed $3 Actually returned. $30/3 = $10 per person After refund of $5.00 and knowing the total cost of the room now was at $25.00 for 3 people. Therefore, $30 (orig)-$5 (refund or "Returns and Allowances") = $25 (Actual room price). $25/3 = $8.33333... (w/3 repeating therefore $8.33 rounded) per person. $3/3 = $1.00 per person refund. $8.33+$1.00 = $9.33 (keep in mind rounding) actually paid per person $9.3333333...*3 = $28.00 $28.00 + $2.00 pocketed = $30.00 Whew! So much for making a phone call with a buck like they advertise! BTW, from a previous post of mine in a thread here in O/T, has anyone figured out the mathimatical formula for a "SNIFFLE" from the problem I gave?

Yeah, but after the bellhop gives them each a dollar, each man is down for $9, not $9.33.

At least I "mathmatically" have found the "magical" disappearing dollar via the long lost art (in my book anyways) through the use of accounting principles.

quote Originally posted by FieroJoe: 15 and 20 G's!!! Holy Sh*t! So, whats the percentage of people that pass out? Do the chutes automatically deploy? I would hope so incase you passed out. I thought that after about 10 G's things in your brain start shutting down if you can't hold enough blood up there.

I beleive thats only sustained....

in a car accident the forces are greater then 10 g's

Here's another interesting tid-bit.

Black holes do grow in size the more matter they "absorb". It has been calculated that if all matter in the known universe was injected into a black hole, the black hole would grow to the same size as... the known universe.

So our universe could actually be a black hole and we wouldn't know it.

JSocha, Will's answer was more precise, easier to follow, and equally as correct.

From this I can conclude... Will would never make a good consultant.

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Once we have all the bugs ironed out we'll be running on flat bugs.

9 or 10 Gs is most that average person can handle.(which is good since a plane can come apart pretty ez) 3 Gs can pull the wings off a Cessna with no problem

[This message has been edited by rogergarrison (edited 07-07-2001).]