IIT JEE , AIEEE Forum - Physics , Mechanics

sravan

hai every one.

sravan

A variable capacitor is connected to two terminals of a battery of electromotive force E. The capacitor initially has a capacitance C(0) and charge q(0). The capacitance is caused to change with time so that current I is constant. Calculate the power supplied by the battery, and compare it with the time rate-of-change of the energy of the capacitor. Account for any difference.

sravan

Once in a blue moon the moon looks blue or green or purple. Why?

sravan

Not so many years ago there was no order of magnitude estimate of the age of the planet Earth. Edmund Halley (yes, that's the "comet guy") wrote an article in Philosophical Transactions of the Royal Society of London, 29, 296 (1714), where he observed that lakes that emit no rivers (such as Dead Sea, or Caspian Sea) are very salty, and thus it is reasonable to assume that rivers bring salt into the lakes. He further claimed that "'tis not improbable that the ocean it self is become salt from the same cause." Consequently, by measuring the salinity of the oceans and by determining the amount of salt brought by rivers every year, one could estimate the age of the Earth. Halley lacked the data to actually perform an estimate of the age of the Earth using his method. Halley's assumptions are wrong, but nevertheless it was a nice try for his time. What would be the age of Earth according to Halley's method?

sravan

A heavy brick is falling from a height of 1 meter, hits a tennis ball and jumps back to the height of (almost) 1 meter. (We assume that the mass of the tennis ball is negligible compared to the mass of the brick. The collision with the ball is assumed to be elastic, i.e. there is no energy loss.) To what height will the tennis ball jump?

sravan

At what speed will a tennis ball be able to break a glass window?

sravan

A stone falls into the water and water drops are splashed. Why do the water drops fly upwards? Does the maximal height reached by the drops depend (primarily) on the size of the stone or on its speed? What is the maximal height?

sravan

An electrostatic potential has been measured everywhere outside a sphere of radius R. It was found that the potential is spherically symmetric, i.e. depends only on the distance r from the center of the sphere, and is given by the expression A/r, where A is some constant. No measurement of the potential inside the sphere has been performed. What can you say about the charge distribution inside the sphere.

sravan

What movement should be performed by a person rotating a hoop round his body?

sravan

How many drops are there in a cubic centimeter of fog if the visibility is 100m and the fog disappears within an hour.

sravan

I have six questions:

How long is a particle accelarator.
Are there weapons 40 times stronger than the fatman and little boy atomic bombs used in World War 2.
What does E=mc^2 mean?.
Does electricity in general move at the speed of light?
How was fusion discovered? Is it true that the sun is a ball of hydrogen that is in a fusion chain reaction?
How can you become a scientific worker at fermilab?

sravan

"My wife and I are having a friendly dispute over the cost of operating electric light bulbs. Some folks insist that there is no friction involved in electricity. Wouldn't it be nice if it did? Anyway, who could explain the facts with this dilemma?"

sravan

"I recently read an article that made reference to something called Zero Point Energy. It said that every point in space can never be void of all energy. Could you expand on what the Zero Point Energy theory is?"

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