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Gravity and Galileo

How Galileo gave acceleration due to gravity before Newton discovered gravity . exactly what happen
Asked Nikhil

Colorized engraving after Enoch Seeman's 1726 ...

Newton stated the Universal Law of gravitation and explained why objects fall to earth when dropped.

But objects were falling even before Newton explained it.

The concept of speed and velocity was known before the Law of Gravitation was formulated.

Photoelectric effect


I wanted to to know that why the attraction of electrons towards the positive plate of the the CRT is not taken into account in the Einstein’s explanation of the photoelectric effect and only the velocity imparted by the striking photon is considered.


English: German-born theoretical physicist Alb...



Amit Singh


I request you to kindly read the story well. Every aspect is dealt in detail. Please go thoroughly through the text material or the link to photoelectric effect provided in this page.




Don’t believe in rumours. CBSE has not yet finalized the dates. Do not panic. CBSE will not Prepone exams by one month. The exams will start as usual only.

The Nobel Prize in Physics 2013 Announced

The Nobel Prize in Physics 2013 was awarded jointly to

François François Englert (Born: 1932
Peter W. Higgs
Peter W. Higgs (Born: 1929)
Englert and Peter W. Higgs “for the theoretical discovery of a mechanism that contributes to our understanding of the origin of mass of subatomic particles, and which recently was confirmed through the discovery of the predicted fundamental particle, by the ATLAS and CMS experiments at CERN’s Large Hadron Collider”

François Englert and Peter W. Higgs are jointly awarded the Nobel Prize in Physics 2013 for the theory of how particles acquire mass. In 1964, they proposed the theory independently of each other (Englert together with his now deceased colleague Robert Brout). In 2012, their ideas were confirmed by the discovery of a so called Higgs particle at the CERN laboratory outside Geneva in Switzerland..

The awarded theory is a central part of the Standard Model of particle physics that describes how the world is constructed. According to the Standard Model, everything, from flowers and people to stars and planets, consists of just a few building blocks: matter particles. These particles are governed by forces mediated by force particles that make sure everything works as it should.

The entire Standard Model also rests on the existence of a special kind of particle: the Higgs particle. This particle originates from an invisible field that fills up all space. Even when the universe seems empty this field is there. Without it, we would not exist, because it is from contact with the field that particles acquire mass. The theory proposed by Englert and Higgs describes this process.

On 4 July 2012, at the CERN laboratory for particle physics, the theory was confirmed by the discovery of a Higgs particle. CERN’s particle collider, LHC (Large Hadron Collider), is probably the largest and the most complex machine ever constructed by humans. Two research groups of some 3,000 scientists each, ATLAS and CMS, managed to extract the Higgs particle from billions of particle collisions in the LHC.

Even though it is a great achievement to have found the Higgs particle — the missing piece in the Standard Model puzzle — the Standard Model is not the final piece in the cosmic puzzle. One of the reasons for this is that the Standard Model treats certain particles, neutrinos, as being virtually massless, whereas recent studies show that they actually do have mass. Another reason is that the model only describes visible matter, which only accounts for one fifth of all matter in the cosmos. To find the mysterious dark matter is one of the objectives as scientists continue the chase of unknown particles at CERN.
Download and read more information here

“The Nobel Prize in Physics 2013”. Nobelprize.org. Nobel Media AB 2013. Web. 8 Oct 2013.

Hot air rises up; but how?

We used to say that hot air is lighter and so it rises up. But around the hot air, there is cold air. So, how did the cold air allow the hot air to rise up.


Asked by Rashmi and Srushti of class VIII B, KV AFS Bidar.




A pair of Hopper balloons.


You might have seen that helium of hydrogen filled balloon rising up. Also remember the case of hot air balloons. It is the same process here too.


First of all, the air is a fluid and the molecules are free to move as there is plenty of space between the molecules. So, when the air below becomes hot and lighter, they can easily go up through the empty space in between the cold and heavier molecules. the space vacated by the hot molecules are immediately occupied by the comparatively heavier cold molecules.




Does Newton’s Third Law apply on throwing butter on a wall?

Newton’s third law of motion states that

“When we throw any object on anything, that thing also pushes back with the same force. But when we throw butter on the wall, it sticks on the wall. Why?”

Asked by Akshit and Koushal from Class VII A from Kendriya Vidyalaya Air Force Station Bidar, Karnataka



I feel that there is some misconception/misunderstanding here.

A line drawing of two ice skaters demonstratin...

Newton’s Third law states that whenever two bodies interact each other, the force exerted by one body on the other is equal and opposite to the force exerted by the second body on first. These forces are simultaneous and are exerted on different bodies. tha is; the force exerted by the first body is acting on the second body and the force exerted by the second body is acted on the first body.

It doesn’t matter whether the body sticks to the other body or bounces back. We are concerned here with force and not with the motion.

When handful of butter (or clay) is thrown on to the wall, the ball of butter exerts some force on the wall. The wall exerts an equal force simultaneously. But the adhesive force between the wall and butter is more than the force acting on butter which tries to detach it. So it is not detached.

When a rubber ball thrown on the wall, the force exerted by the wall on the ball compresses it. Due to the elastic nature of the ball, it tries to bring the shape back to original and this makes it bounce back. The force exerted on the wall due to the bouncing ball is double that of a clay/butter ball of same mass hitting the the wall with same speed; because, the rubber ball requires the force to bounce back too.

Also refer to http://hyperphysics.phy-astr.gsu.edu/hbase/truckc.html#c1



Is time always a measurement of movement of matter

Is the oscillation of energy levels of caesium in atomic clocks a form of motion (i. e. is time always a measurement of movement of matter)?

asked Gary Wederspahn


The Oscillations in cesium clock is not mechanical. the radiation emission frequency between the two hyperfine levels of the atom is used as the standard for measuring time. Due to the fact that the standardisation of time is based on radiations, the atomic clocks are also called radio clocks.

Caesium clocks are the most accurate commercially produced time and frequency standards, and serve as the primary standard for the definition of the second in SI (the metric system). By definition, radiation produced by the transition between the two hyperfine ground states of caesium (in the absence of external influences such as the Earth’s magnetic field) has a frequency of exactly 9,192,631,770 Hz. That value was chosen so that the caesium second equalled, to the limit of human measuring ability in 1960 when it was adopted,

Very accurate clocks can be constructed by locking an electronic oscillator to the frequency of an atomic transition. The frequencies associated with such transitions are so reproducible that the definition of the second is now tied to the frequency associated with a transition in cesium-133:

1 second = 9,192, 631,770 cycles of the standard Cs-133 transition

Cs Atomic clock
Cs Atomic clock

Ref http://hyperphysics.phy-astr.gsu.edu/hbase/acloc.html#c2

The oscillation in an atomic clock is between the nucleus of an atom and the surrounding electrons. This oscillation is not exactly a parallel to the balance wheel and hairspring of a clockwork watch, but the fact is that both use oscillations to keep track of passing time. The oscillation frequencies within the atom are determined by the mass of the nucleus and the gravity and electrostatic “spring” between the positive charge on the nucleus and the electron cloud surrounding it.

Ref: http://web.mit.edu/scicom/www/atomicclock.html



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