What speed will an object fall?

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The discussion centers on calculating the speed of a falling object, emphasizing that the speed is independent of weight when ignoring air resistance. A formula derived from kinetic and potential energy principles is presented: v = (2gh)^0.5, where v is the final velocity, g is the acceleration due to gravity, and h is the height. It is noted that this formula holds true only when drag forces are neglected, which is often not the case in real-world scenarios. Participants clarify that while mass does not affect falling speed, drag is influenced by an object's geometry. Ultimately, the conversation highlights the complexities of real-life physics versus theoretical calculations.
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I am looking for a formula to determine what speed an object will fall with a known height and weight. For example a 220 pound man falls from 65 ft, what speed will he be going when he hits the ground?
 
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You do know that the speed an object falls is independent of its weight...right? The equations for constant acceleration are very well known in intro physics courses.

http://selland.boisestate.edu/jbrennan/physics/notes/Motion/constant_acceleration_formulas.htm

http://www.juliantrubin.com/bigten/galileofallingbodies.html
 
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FredGarvin said:
You do know that the speed an object falls is independent of its weight...right?
I know that you know this Fred, but for the benefit of the OP I will mention the caveat that an objects' instantaneous velocity is only independent of mass provided that the effects of drag are ignored.
 
Hootenanny said:
I know that you know this Fred, but for the benefit of the OP I will mention the caveat that an objects' instantaneous velocity is only independent of mass provided that the effects of drag are ignored.
True. However it should be pointed out that drag is not proportional in any way to mass either. It is a function of geometry.
 
ATCLanser said:
I am looking for a formula to determine what speed an object will fall with a known height and weight. For example a 220 pound man falls from 65 ft, what speed will he be going when he hits the ground?

There is a simple derivation for the formula below.
The kinetic energy at the moment the object hits the ground is 0.5mv^2 which is equal to its potential energy at given height "h"
Thus 0.5mv^2=mgh
And v=(2gh)^0.5 which is independant of the weight.
 
aniketp said:
There is a simple derivation for the formula below.
The kinetic energy at the moment the object hits the ground is 0.5mv^2 which is equal to its potential energy at given height "h"
Thus 0.5mv^2=mgh
And v=(2gh)^0.5 which is independant of the weight.

This is only true if the drag force is ignored (as pointed out previously by Hootenanny and Fred). In real life it is not normally ignored.

CS
 

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