Acceleration due to gravity question.

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Discussion Overview

The discussion revolves around the concept of acceleration due to gravity, specifically addressing the nature of acceleration and speed in the context of falling objects. Participants explore the definitions and implications of gravitational acceleration, as well as mathematical equations related to motion under gravity.

Discussion Character

  • Exploratory
  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • Some participants express confusion about whether acceleration increases over time or if it remains constant, with one participant suggesting that acceleration might be increasing by 10 m/s every second.
  • Others clarify that it is the speed that increases, while the acceleration due to gravity remains constant at approximately 10 m/s².
  • There is a question about the meaning of "per second" in the phrase "10 meters per second per second," with participants seeking clarification on the distinction between speed and acceleration.
  • Participants inquire about mathematical equations that describe the rate of acceleration due to gravity, with one mentioning an equation involving t squared.
  • Equations related to falling motion under gravity are presented, including the constant acceleration and the equations for speed and distance fallen over time.

Areas of Agreement / Disagreement

Participants generally agree that acceleration due to gravity is constant, but there is some confusion regarding the terminology and implications of acceleration versus speed. The discussion includes multiple viewpoints on the interpretation of these concepts, and no consensus is reached on the initial confusion about acceleration increasing over time.

Contextual Notes

Some participants express uncertainty about the definitions of speed and acceleration, and there are unresolved questions regarding the implications of the terminology used in physics. The discussion also touches on the mathematical representation of motion under gravity, but not all participants may fully understand the equations presented.

Who May Find This Useful

This discussion may be useful for individuals with a casual interest in physics, particularly those seeking to understand the concepts of acceleration and speed in the context of gravity, as well as those looking for mathematical descriptions of motion under gravitational influence.

inertiaforce
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I am not a physics professional. I just have found a casual interest in physics. I have a question about gravity.

Gravity accelerates objects at 9.8 meters per second, per second. I will round this off to 10 meters per second per second.

Does this mean that for every second, the rate of acceleration increases? In other words, after the 2nd second, the rate of acceleration is 20 meters per second? After the third second, the rate of acceleration is 30 meters per second? Is the RATE of acceleration increasing by 10 meters per second for every second so that after 20 seconds the rate of acceleration would be 200 meters per second?
 
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inertiaforce said:
I am not a physics professional. I just have found a casual interest in physics. I have a question about gravity.

Gravity accelerates objects at 9.8 meters per second, per second. I will round this off to 10 meters per second per second.

Does this mean that for every second, the rate of acceleration increases? In other words, after the 2nd second, the rate of acceleration is 20 meters per second? After the third second, the rate of acceleration is 30 meters per second? Is the RATE of acceleration increasing by 10 meters per second for every second so that after 20 seconds the rate of acceleration would be 200 meters per second?
No, it's the speed that is increasing, not the acceleration. Speed is in meters per second and that speed increases as an object falls. The acceleration is the rate of change of that speed, in meters per second per second. That acceleration is a constant.
 
Doc Al said:
No, it's the speed that is increasing, not the acceleration. Speed is in meters per second and that speed increases as an object falls. The acceleration is the rate of change of that speed, in meters per second per second. That acceleration is a constant.

Ok. So the acceleration remains at 10 meters per second then?

If that's true, why is it said that the rate of acceleration due to gravity is 10 meters per second PER SECOND? Why is that 2nd "per second" there? Why don't they just say the rate of acceleration is 10 meters per second? Why 10 meter per second PER SECOND?
 
inertiaforce said:
Ok. So the acceleration remains at 10 meters per second then?

If that's true, why is it said that the rate of acceleration due to gravity is 10 meters per second PER SECOND? Why is that 2nd "per second" there? Why don't they just say the rate of acceleration is 10 meters per second? Why 10 meter per second PER SECOND?
Meters per second is the units for speed, not acceleration.

The acceleration is 10 m/s per second. That means every second the speed increases by 10 m/s.
 
Thanks for clearing that up. I had some confusion about whether it was just the speed that was increasing, or both the speed and the rate of the acceleration.

Seems like you've cleared that up for me.

Is there a math equation that describes the rate of acceleration due to gravity? My father told me he had seen an equation with t squared in it. Are you familiar with any such equation?
 
inertiaforce said:
Thanks for clearing that up. I had some confusion about whether it was just the speed that was increasing, or both the speed and the rate of the acceleration.

Seems like you've cleared that up for me.
Good!

Is there a math equation that describes the rate of acceleration due to gravity? My father told me he had seen an equation with t squared in it. Are you familiar with any such equation?
Here are some equations that describe falling motion under gravity.

a = g = 9.8 m/s/s. (This just says that the acceleration is a constant 'g', which is 9.8 m/s/s.)

v = a*t = g*t (This gives the speed of a falling body at any time after it's dropped. So, after 1.5 seconds, v = 9.8*1.5 = 14.7 m/s.)

s = 1/2*a*t^2 = 1/2*g*t^2 (This is the equation you were looking for. It gives the distance fallen, s, as a function of time. So, after 1.5 seconds, the object falls a distance of s = .5*9.8*1.5^2 = 11 m.)
 
That sounds like the equation for the distance an object falls under the influence of gravity. If you drop an object from rest, after t seconds it has fallen the distance
$$s = \frac{1}{2}gt^2$$
(Added: Doc Al beat me to it while I was typing...)
 
jtbell said:
(Added: Doc Al beat me to it while I was typing...)

haha
 

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