# m4rc

Senior Members

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• Birthday 05/31/1972

## Profile Information

• Location
Australia
• College Major/Degree
Physics
• Favorite Area of Science
Physics-experimental
• Occupation
physicist

• Meson

12

1. ## Infinite infinities

An example that infinity/infinity=anything let a=the total number of integers let b=the total number of even integers both a and b are infinite but a is twice as large as b so, a/b=infinity/infinity=2 and b/a=infinity/infinity=0.5 The reason we get this is that there are many different ways to define infinity.
2. ## Why is time considered to be dilated, rather than molecular activity slowed down?

I have had a physics professor that had unconventional ideas about relativity. He considered time dilation more as a slowing of clocks than a change in the flow of time. He has shown that time dilation can be considered to be the slowing down of clocks as a result of the mass change of the object http://www.newtonphysics.on.ca/kinetic/length.html . For example, as an object moves at close to the speed of light, it's mass is different, and so is the mass of the electrons in the object. This increased mass of the electrons would make the electrons move closer to the centre of their atoms and also move more slowly (this is the calculation of the Bohr radius). Any clock that is based on the motion of electrons (and all clocks are) would be slowed down in the same way. In his opinion this explains both the length contraction and time dilation. As far as I know there is no current experimental way of distinguishing the results of this theory, however I find this explanation more rational than the conventional theories which although accurately model the situation don't explaining things very well.
3. ## Astrology!!! 100% Foolproof science!!!!

I enjoy reading about how ancient cultures that used astrology in ways that science eventually found legitimate. Most of the legitimate application of astrology involved looking at the stars to determine the time of the year, which would be used to determine the best time to plant seeds or harvest. I suspect that these early successes of astrology encouraged the astronomers to make predictions that we now know has nothing to do with the positions of the stars.
4. ## Wheatstone bridge

A Wheatstone bridge is a particular combination of resistors. Try wikipedia for more details. http://en.wikipedia.org/wiki/Wheatstone_bridge
5. ## Math Question

I am not certain which force you are trying to calculate. The Force that the rotating object will have on the post will be equal to the force required to keep that object rotating. F=mrw^2, where F is the force in Newtons, m is the mass in kg, r is the radius of rotation of the object in meters and w is the angular velocity in radians/second. This will apply if the size of the rotating object is small compared to r. If it is not, then give a good description of the object rotating. This will be the force where the rotating object meets the axis of rotation. If you want to calculate the force that this would have in the ground, you will need to consider the leverage that your design will give you.
6. ## what is the smallest particles that all particles are made of

Particles are the smallest things that have been observed. Some particles like the electrons, muons, and neutrinos are considered elementary (not made up of smaller particles). Other particles like the proton, neutron and others are thought to be made up of quarks. No quarks have been observed in isolation, but their existence is expected. Even more theoretical is the concept of vibrating strings. The main concept behind string theory is that the everything is made of vibrating strings of some kind.
7. ## I am in need of help: equations and references

If you require a precise answer then it will be difficult The first effect is that sound spreads out as it moves away from the source The other cause for attenuation is absorption which will be more important in materials. In matter, I suppose that the absorption of sound waves will decay exponentially with distance. The spreading out of the wave: The reduction in intensity due to this effect is I=P/A , where I=sound intensity, P=power of the source of sound, A=area over which the sound is spread over. The intensity of sound can be measured in watts per square meter. The threshold of hearing is about 10^-12 W/m^2, whispering is at 10^-10 W/m^2 and a rock concert may be 0.1W/m ^2. If you are in a wide open space, then you the area you will use is the area of a sphere with a radius equal to the distance between you and the source. A=(4/3) pi r^3 It would be difficult to calculate the attenuation of sound with distance in buildings because sound can reflect of walls and be channeled down hallways. Depending on what you're trying to calculate, it might be important to know that the ear's sensitivity to sound intensity varies with sound intensity. When comparing perceived sound intensities, you should express the intensity in decibels where: Intensity in db= (10dB) Log(I/10^-12W/m^2)
8. ## Light and Gravity

Interesting article. I can see where you may have been confused by the article. Both gravity and matter can affect the propagation of light. The effect of gravity on light: A black hole can change the direction of light (deflection of any angle) but this will be without changing its speed. The photon will gain energy as it moves towards a black hole (blue shift) or it will lose energy if it is moving away from a black hole (red shift). However for light near a black hole the speed of light is constant. Slowing down light in a medium When people say that the speed of light is lower in matter, the mean that the distance traveled over the time interval is lower. What is happening is that as the light passes though matter, it gets absorbed then re-emitted after a short delay. This occurs multiple times. As it travels from one atom to the next it is traveling at the speed of light, but because of all the delays, it has a lower average speed . The subject of the article involves strange effect that occur when a liquid is flowing faster than the (average) speed of light that liquid.
9. ## force = mass x acceleration

If something is moving at a constant velocity then the sum of all the forces acting on it will be zero. If something collides with your body, the object won't stay at the same velocity in this situation. The object will slow down (thus have an acceleration). The magnitude of the force will be equal to the product of the mass of the object and its acceleration.
10. ## Pulley Problem

The question is not that complicated. The tension is how much force that the rope is applying to the system. Therefore, in this case, the tension is equal to P.
11. ## A conjecture: pi changes with time

Ok I see what you're saying now. ( I initially took your post as a joke, sorry about that) In curved space, a curved diameter will be longer than a straight diameter in flat space. So depending on the radius of curvature of space, the ratio of the circumference to the curved diameter will be somewhere between 2 and our currently accepted value for pi.
12. ## A conjecture: pi changes with time

More evidence of a variable value for pi The value of pi is clearly increasing with time. In biblical times, the value of pi was 3. If the circumference was 30 cubits and the diameter was 10 cubits, then pi was 3.
13. ## Question concerning AC circuits

Your answer would have been valid if the question did not specify that the graph must be shifted to the left. However since it does specify this, they are looking for the first value of t0 that is positive. You will find that "40 cos(100pi t +2pi)" is equivalent to "40 cos(100pi t)" because it is shifted by one full period. You can always add one (or multiple) period(s) to get a phase factor with the correct sign.
14. ## heat retention of materials

No. There are many examples of good insulators with a low heat capacity. For example, many thermos bottles have a vacuum layer which would have a very low heat capacity but provides excellent insulation. A good insulator will have a low thermal conductivity which is different than the heat capacity. The heat capacity is a measure of how much heat an object can absorb, while the thermal conductivity is a measure of how much heat an object can transmit through itself.
15. ## "Work" Word Problems

I assume that you mean how do you calculate mechanical work. If you apply a force to move an object then the work done will be the product of the force and the displacement of the object. W=Fd (if F and d are in the same direction. It can be more complicated if the force and displacement are in different directions, in which case: W=Fd cos(theta) where theta is the angle between the force and the displacement.
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