Ruler+hammer balance: 3 stages

In summary, the conversation discusses a video on the Discovery Channel that shows a trick with three hammers and three rulers. The participants in the conversation analyze the physics behind the trick and explain that it is possible due to the distribution of mass within the objects. They also mention that the experiment is in line with the laws of physics and is not something fundamentally new.
  • #1
Newtonfalls
6
0
Hi,

yesterday i saw this video on discovery channel.
<link to video deleted>
in the documentation it was said that this trick with the three hammers and
three rulers doesn´t match with actual laws of physics! does anyone can give more
information about this?
 
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  • #2
Hi Newtonfalls,

Any object will escape falling over an edge as long as its centre of mass is supported. The position of the COM depends on the mass distribution within the object. It looks like the effect of adding the hammer is to alter this distribution. More specifically, it looks like the first hammer is added such that the centre of mass of the ruler-hammer system moves under the table where it is supported. A hammer is a useful object to do this because most of its mass is concentrated in one end. As long as all the hammers are arranged to keep enough mass far enough under the table so that more force pulls down into the table than into empty space, it should be possible to extend the system like in the video.

The idea of disproving all laws of physics seems like a bit of sensationalism on the part of the Discovery Channel, since I'm sure PF would be abuzz if that really were true :P
 
  • #3
With one hammer, you can find the trick everywhere. The extension looks nice, but it is nothing fundamentally new. The second hammer has to be much lighter than the first one, and the third has to be much lighter than the second one, so all rulers stay balanced.

I changed the thread title. The experiment is well in agreement with physics, it just can look counterintuitive if you don't think about the mass distributions.
 
  • #4
 
  • #5
mfb said:
With one hammer, you can find the trick everywhere. The extension looks nice, but it is nothing fundamentally new. The second hammer has to be much lighter than the first one, and the third has to be much lighter than the second one, so all rulers stay balanced.

I changed the thread title. The experiment is well in agreement with physics, it just can look counterintuitive if you don't think about the mass distributions.

This demonstrates the same principle in a clearer fashion, where density is more even. It is also much more impressive in my book:
 
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Likes mfb
  • #6
I well remember Balance Goddess when it first appeared. Most impressive.
 

1. How does the ruler+hammer balance experiment work?

The ruler+hammer balance experiment works by using a ruler as a lever and a hammer as the weight. The ruler is placed on a fulcrum and the hammer is hung from one end. The distance from the fulcrum to the hammer is measured, and then the ruler is flipped over so the hammer is now on the other end. The distance from the fulcrum to the hammer is measured again. The ratio of the two distances is used to determine the balance point of the ruler, which can then be used to calculate the weight of the hammer.

2. What are the three stages of the ruler+hammer balance experiment?

The three stages of the ruler+hammer balance experiment are: measuring the distance from the fulcrum to the hammer when it is on one end of the ruler, flipping the ruler and measuring the distance from the fulcrum to the hammer on the other end, and using the ratio of the two distances to calculate the balance point of the ruler.

3. What is the purpose of the ruler+hammer balance experiment?

The purpose of the ruler+hammer balance experiment is to demonstrate the concept of balance and how it can be used to determine the weight of an object. It also allows for practicing measurement and calculation skills.

4. What factors can affect the accuracy of the ruler+hammer balance experiment?

The accuracy of the ruler+hammer balance experiment can be affected by several factors, such as the precision of the ruler and the placement of the fulcrum. Other factors include the weight distribution of the hammer and any external forces acting on the ruler during the experiment.

5. How can the ruler+hammer balance experiment be used in real-life applications?

The ruler+hammer balance experiment can be used in real-life applications to measure the weight of small objects, such as jewelry, coins, or spices. It can also be used in industries that require precise measurements, such as pharmaceuticals or food production. Additionally, the concept of balance and the use of a lever can be applied to engineering and construction projects.

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