Gravity: Explaining the Mysteries of Weight and Falling

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In summary, the conversation discusses the concept of objects falling at the same rate on Earth due to gravity, with the exception of air resistance. The teacher demonstrated this by showing that when crumpled to the same size, a flat paper and a golf ball fall at the same rate. However, the conversation also raises two questions about this concept, specifically why a book falls faster than a piece of paper of the same shape and size, and if weight or mass play a factor in the rate of falling. The expert summarizes that in the atmosphere, objects of different mass fall at different rates due to the effects of air resistance. Additionally, at low velocities, the difference in weight is not noticeable, allowing for the teacher's demonstration. The summary also
  • #1
Jow
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I love physics, but I find that I am ignorant about some of the more basic concepts, so forgive me if this question may sound a bit foolish.
My teacher the other day demonstrated that all objects fall at the same rate on earth. The only reason things don't seem to follow this rules is because of air resistance. He showed that when flat, paper falls slower than a golf ball, but when crumpled to the size of the golfball they fall at the same rate.
I have two questions about this. I know that a book will fall faster than a piece of paper of the same shape and size. I tested at home to make sure. If it has nothing to do with weight than why does the book fall faster?
Also, shouldn't weight, or mass make a difference. If F = Gm1m2 / r^2, than surely the more massive something is than the faster it will fall. My textbook answers neither of these questions, so it would be much aporeciated if you could answer them. Thank you.
 
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  • #2
Hi Jow,

For your first question, you can't simply neglect the weight or the mass of the book because its already clear that F = ma.

Its already stated that mass is related to acceleration (gravity).
 
  • #3
Jow said:
but when crumpled to the size of the golfball they fall at the same rate.
That is not true. Two objects of exactly the same shape/size, but different mass fall at different rates in the atmosphere. Only in vacuum the acceleration is the same, because gravity is the only force acting and proportional to mass. But air resistance is not dependent of mass. At the same velocity the opposing air resistance is the same for both objects, but the weight is different. So the net force and acceleration are different. At low velocities the drag is low, and the difference is not noticeable which allows the teacher to fool the students.
 
  • #4
Jow said:
If F = Gm1m2 / r^2, than surely the more massive something is than the faster it will fall. My textbook answers neither of these questions, so it would be much aporeciated if you could answer them. Thank you.
And F=m1a. Combine both equations, and you get a = Gm2/r^2, which depends on the mass of Earth but not on the mass of the falling object. If the falling object has a mass similar to earth, you would have to take the motion of Earth into account, but that can be neglected for any realistic experiment.
 
  • #5
https://www.physicsforums.com/showthread.php?t=511172 [Broken]
 
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1. What is gravity?

Gravity is a natural phenomenon by which all objects with mass are brought towards each other. It is the force that keeps planets in orbit around the sun and causes objects to fall towards the Earth.

2. How does gravity work?

Gravity is a result of the curvature of space and time caused by the presence of mass or energy. The larger the mass, the stronger the gravitational pull. This pull is what keeps objects in orbit and causes them to fall towards a larger mass.

3. Who discovered gravity?

Sir Isaac Newton is credited with discovering the laws of gravity in the late 17th century. However, the concept of gravity has been observed and studied by ancient civilizations such as the Greeks, Egyptians, and Chinese.

4. How is gravity related to weight?

Weight is a measure of the force of gravity on an object. The more massive an object is, the more gravitational force it will experience and the more it will weigh. This is why objects appear to weigh less on the moon, where the force of gravity is weaker.

5. Can gravity be manipulated or controlled?

Gravity is a fundamental force of nature and cannot be manipulated or controlled. However, its effects can be counteracted or simulated through technologies such as rockets and artificial gravity in space stations.

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