science_geeks
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Hi everyone,

I'm trying to write a report on free falling objects, but I'm struggling to understand why the theory of free-fall, drag and air resistance is so important to physics?

Please can someone give me some more info?

Thanks in advance
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PolarBear27
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Physics is the study of matter and energy and their behaviour with eachother. When investigating how an object falls you need to understand the conditions taking place. Free fall occurs when weight is the only force acting on the object (gravity is the only acceleration). This doesn't happen on earth because we have air which creates a resitive force on the object (the object is bombarded with air particles), known as drag or air resistance. Air resistance/drag and free fall are important for understanding physics because they are conditions which affect the behaviour of an object. The goal of physicists is to undertand the behaviour of said objects, therefore it is important to understand these theories.
I hope this was helpful and good luck with your report.
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science_geeks
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(Original post by PolarBear27)
Physics is the study of matter and energy and their behaviour with eachother. When investigating how an object falls you need to understand the conditions taking place. Free fall occurs when weight is the only force acting on the object (gravity is the only acceleration). This doesn't happen on earth because we have air which creates a resitive force on the object (the object is bombarded with air particles), known as drag or air resistance. Air resistance/drag and free fall are important for understanding physics because they are conditions which affect the behaviour of an object. The goal of physicists is to undertand the behaviour of said objects, therefore it is important to understand these theories.
I hope this was helpful and good luck with your report.
Thank you so much, this is really helpful and it's helped understand why free-fall's so important!

Just another quick question, I know you said that (free-fall) doesn't happen on Earth because we have resistive forces such as air resistance and drag so what would a real life example of free-fall be?

And so, the experiment I did was measuring the fall times of two different objects (one was a steel ball the other was a plastic one) at different heights. I have to be totally honest, I didn't quite get the point of it at the time but from the research I've done I think I've realised that once the object comes out of free-fall motion (so till gravity stops being the only force acting on it) air resistance begins to act on it so that the object experiences/reaches (not sure which one) terminal velocity.

Terminal velocity is when air resistance is equal to the weight of the object. Upward drag = mg. I could be wrong but, does this follow Newton's second law where in, all forces are balanced?

Sorry to bombard you with a ton of questions, but what was Gallelio's Theory and what did it help prove? Was it that heavier objects fall faster?

Thanks so much!
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PolarBear27
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(Original post by science_geeks)
Thank you so much, this is really helpful and it's helped understand why free-fall's so important!

Just another quick question, I know you said that (free-fall) doesn't happen on Earth because we have resistive forces such as air resistance and drag so what would a real life example of free-fall be?

And so, the experiment I did was measuring the fall times of two different objects (one was a steel ball the other was a plastic one) at different heights. I have to be totally honest, I didn't quite get the point of it at the time but from the research I've done I think I've realised that once the object comes out of free-fall motion (so till gravity stops being the only force acting on it) air resistance begins to act on it so that the object experiences/reaches (not sure which one) terminal velocity.

Terminal velocity is when air resistance is equal to the weight of the object. Upward drag = mg. I could be wrong but, does this follow Newton's second law where in, all forces are balanced?

Sorry to bombard you with a ton of questions, but what was Gallelio's Theory and what did it help prove? Was it that heavier objects fall faster?

Thanks so much!
Hi! Sorry for the late reply. True free fall will occur in a vacuum (so there are no particles to cause air resistance) when the only force acting on the object is the weight. You could do this on earth by dropping an object in a vacuum chamber.
When an object is falling on earth, as its velocity increases, the drag force acting on it will increase. Eventually, the weight of the object falling will be equal to the drag force acting on it. Therefore, it follows Newton's Law because the resultant force is 0, so the acceleration is 0, so the maximum velocity has been reached (maximum velocity= terminal velocity).
Galileo's theory of falling objects proves that objects will fall at the same acceleration irrespective to their mass. This is because W=ma when an object is falling, so mg=ma, so g=a. The masses cancel out so the acceleration is always 9.81m/s^2. Aristotle's theory was that the acceleration of an object is proportional to its mass (this is not true).
I hope this helps
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science_geeks
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(Original post by PolarBear27)
Hi! Sorry for the late reply. True free fall will occur in a vacuum (so there are no particles to cause air resistance) when the only force acting on the object is the weight. You could do this on earth by dropping an object in a vacuum chamber.
When an object is falling on earth, as its velocity increases, the drag force acting on it will increase. Eventually, the weight of the object falling will be equal to the drag force acting on it. Therefore, it follows Newton's Law because the resultant force is 0, so the acceleration is 0, so the maximum velocity has been reached (maximum velocity= terminal velocity).
Galileo's theory of falling objects proves that objects will fall at the same acceleration irrespective to their mass. This is because W=ma when an object is falling, so mg=ma, so g=a. The masses cancel out so the acceleration is always 9.81m/s^2. Aristotle's theory was that the acceleration of an object is proportional to its mass (this is not true).
I hope this helps
This is perfect! Thanks so much, in one of my results I've drawn a graph of time^2 against the height displaced but I was expecting a parabola but ended up with a straight line what could be the problem with that? I don't want to include it in my report but I haven't got much choice but to include it. What would you recommend?
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PolarBear27
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(Original post by science_geeks)
This is perfect! Thanks so much, in one of my results I've drawn a graph of time^2 against the height displaced but I was expecting a parabola but ended up with a straight line what could be the problem with that? I don't want to include it in my report but I haven't got much choice but to include it. What would you recommend?
I’m not too sure about this, but I think it’s ok if it’s a straight line because since you used t^2 it’s in the form of y=mx+c. If you use the kinematics equation s= ut + 0.5at^2 (where u=0) you get h=0.5gt^2 (where h=height and g=gravity). So the gradient should be 0.5g, so you can find g by doing 2 x gradient.
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science_geeks
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(Original post by PolarBear27)
I’m not too sure about this, but I think it’s ok if it’s a straight line because since you used t^2 it’s in the form of y=mx+c. If you use the kinematics equation s= ut + 0.5at^2 (where u=0) you get h=0.5gt^2 (where h=height and g=gravity). So the gradient should be 0.5g, so you can find g by doing 2 x gradient.
Awesome, I just thought I was supposed to get a parabola given that the times are all squared.

Also, in my report with the results section do I just put in all my tables and graphs? Do I have to have any written summary of my findings?

Thanks so much for your help with this!!
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PolarBear27
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(Original post by science_geeks)
Awesome, I just thought I was supposed to get a parabola given that the times are all squared.

Also, in my report with the results section do I just put in all my tables and graphs? Do I have to have any written summary of my findings?

Thanks so much for your help with this!!
No worries!
I’d say that the results section should have the tables and graphs, as well as a brief summary of what these results show. I’d also include an evaluation to explain what went well and what didn’t, and how the experiment could be improved.
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science_geeks
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(Original post by PolarBear27)
No worries!
I’d say that the results section should have the tables and graphs, as well as a brief summary of what these results show. I’d also include an evaluation to explain what went well and what didn’t, and how the experiment could be improved.
That sounds great! Thank you so much
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