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# Monthly Archives: May 2017

## Heat requirements for Leidenfrost effect

I had a simple question that I couldn’t find an easy answer to. I have recently been studying the Leidenfrost effect and the effects it has on water. My question is this, is it possible for metals to heat to the Leidenfrost point? I understand that the Leidenfrost point is quite a bit higher than an elements boiling point. This is true for water and easily observed by placing droplets on a skillet that’s already heated. I guess to summarize my question, do metals have a Leidenfrost point and if so would they act the same way water does?

## Deriviation of why mass can be thought of as to act at the centre

http://www.feynmanlectures.caltech.edu/I_13.html
The last equations where Feynman explains why the mass of an object can be taken to be acting at the centre i.e where he has a hollow spheres, in the section ‘Gravitational field of large objects’. I cant understand the following:If we call xx the distance of a certain plane section from the center, then all the mass that is in a slice dxdx is at the same distance rr from PP, and the potential energy due to this ring is −Gm′dm/r..

Also, why are the limits taken as such i.e R-a and R+a. And the part where he explains how the potential is the same inside the sphere.

## Newton’s Third Law..maybe?

Okay, so in this scenario, a girl jumps from the third step of a staircase and lands in the hallway that is at the foot of the staircase and right when she lands, a door that is beneath the staircase cracks open outwardly. The door doesn’t open all the way, but what physics law would be corresponded to the door opening as the girl lands on the ground? Or is it not possible for the door to open outwardly instead of inwardly?

## Need help with this Physics question from electromagnetism

A 20.0 m long wire is carrying a 150.0 mA current parallel to a second wire that is extremely long which carries a current of 250.0 mA in the same direction. These wires are placed 40.0 cm apart in a 5.5 T magnetic field that is directed into the page. Calculate the magnetic force on each wire and indicate the direction of the force. Each of these wires would generate a smaller magnetic field, indicate the direction this magnetic field would travel between the wires.

Mark Dreeson

## Motion on a frictionless surface

Suppose a body is kept on frictionless surface(but gravity os there). If we give a little push to the body , will it continue in state of motion with constant velocity or not..?….if yes then why…?

If the surfaces are totally frictionless theñ on giving a slight push it would be put to motion with uniform velocity. Newtons first kaw is the reason. Since there is no net force acts, velocity should remain constant.
The force due to grsvity acts vrtically downwards and os canceled by the normal reaction

## Ideal gas laws and Physics of the atmosphere

How can you use the ideal gas law as a model to describe the physics of the atmosphere?

and

How does a environment satellite work? How correct are they?

## Observer effect in quantum physics

Hello!

Please clarify the Observer effect in quantum physics  for me.

Is it true that the results of the double-slit experiment with detection of particles at one of the slits collapsing the wave-function depend on whether observer is in the room or not. If the observer is not in the room and the results of the detector are not recorded somehow the wave function is preserved despite detection of particles at the slits by non-conscious detector.

If it is the case, have experiments been conducted to identify whether the observer has to be somehow qualified to understand the contents of the experiment to result in the collapse of the wave function?

Is there a lab open to the public where this mechanism can be observed?

Thank you!
Max

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