Free-fall acceleration

  • Thread starter JohnDubYa
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  • #51
Armo is a failure. It is just constant gravitaional acceleration. no matter what direction its moving....that the only clarification thats necessary. It might be difficult to grasp the concept of accelerating in the opposite direction of movement. but then there is a general comprehension problem as its a basic mechanics concept, similar to braking in a car.
 
  • #52
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Armo is a failure.
You're not exactly subtle, are you?

It is just constant gravitaional acceleration. no matter what direction its moving....that the only clarification thats necessary. It might be difficult to grasp the concept of accelerating in the opposite direction of movement. but then there is a general comprehension problem as its a basic mechanics concept, similar to braking in a car.
That's all fine, but irrelevant to the topic.
 
  • #53
Armo is a friend of mine...its all in jest. Anyway, its true but not irrelevant. the confusing terminoligy comes about when when people dont get that the gravitational acceleration can still be in the other direction even when an object has 0 velocity. my initial cofusion way back when i still had a problem grasping basic mechanics was that the acceleration due to gravity is the same in any case. and the term falling is a reference to acceleration not velocity.
 
  • #54
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I think the orginal post, is refering to say an astronaut, that is in a free fall in space, but not actually falling, he/she is just falling at the same rate the earth is spinning (orbit)...idk just to help you all out, the other word for free fall...under the influnce of a gravtational force
 
  • #55
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Rampant, the problem is that students have associated falling with downward motion all their lives. To assign it to cases where an object is rising is counter-intuitive to THEM.

Take a bunch of schoolchildren outside and throw a rock in the air. On the way up, ask them if the rock is falling. What do you think they will say?

And the idea of falling is ingrained in their heads for 20 years, and now you are going to say that the rock is actually falling, when they "know" that such isn't the case.

One of the complaints that students have about physics is that we use their common-day lingo in odd ways. To them, it is like showing a picture of a rhino and telling them it is an elephant.
 
  • #56
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This discussion regarding free fall has taught me to be sure of the facts before argueing. I apologise i got it wrong.
something can be in freefall if it is going up but it has to be travelling a an angle of 0 degrees. if it is not then it is undergoing projectile motion,which means that the only force acting on it is gravity which is the same as freefall but i think it is important that we do distinguish between the two.
My respect for the forum has increased endlessly and i will be contributing as soon as my new credit card comes through.
regards all and keep on talking. it feeds our brains and gets us thinking
jamie
 
  • #57
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something can be in freefall if it is going up but it has to be travelling a an angle of 0 degrees. if it is not then it is undergoing projectile motion,which means that the only force acting on it is gravity which is the same as freefall but i think it is important that we do distinguish between the two.
You need to work on it a little more. Simple projectile motion IS an example of a body in free fall. An artillery shell shot out of a cannon is in free-fall motion (ignoring air friction).

Free-fall acceleration is defined as motion where the only force acting on the object is gravity. A projectile satisfies this criterion.

I think everyone can see why the term free-fall acceleration leads to errors. :)
 
  • #58
BobG
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You could just say the object's experiencing gravitational acceleration.

Oh, wait. How can it be accelerating if it's slowing down? :confused:

Terminology's a problem, no matter how you slice it. Common language evolves over time, sometimes for good, sometimes for bad (what could be wrong about being a little more specific about exactly what type of acceleration you're experiencing - positive or negative?). Science and math tend to hold their terms constant and wind up using some rather archaic definitions.

I get the same problem explaining orbital element sets. Argument of perigee, true or mean anomaly, flight path angle. If you're creative, you can use three different words for angle in one sentence (argument, anomaly, angle). And just try explaining how the First Point of Aries can be found in the Pisces constellation - you're sure to wind up arguing about when will it be the dawning of the age of aquarius. :rolleyes:
 

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