Skip to main content

Posts

Showing posts from November, 2014

How does GPS(Global Positioning System) work?

Q. How does GPS(Global Positioning System) work?

A. The Global Positioning System (GPS) is a network of about 30 satellites orbiting the Earth at an altitude of 20,000 km. The system was originally developed by the US government for military navigation but now anyone with a GPS device, be it a SatNav, mobile phone or handheld GPS unit, can receive the radio signals that the satellites broadcast.

Wherever you are on the planet, at least four GPS satellites are ‘visible’ at any time. Each one transmits information about its position and the current time at regular intervals. These signals, travelling at the speed of light, are intercepted by your GPS receiver, which calculates how far away each satellite is based on how long it took for the messages to arrive.

Once it has information on how far away at least three satellites are, your GPS receiver can pinpoint your location using a process called trilateration.

Trilateration

Imagine you are standing somewhere on Earth with three satellit…

Why Do We Always See the Same Side of the Moon?

Q: Why does the moon always present the same face to us? I find it impossible to believe that this could happen by chance.

A: Nope, not by chance — it’s pure physics.

For starters, the moon is not stuck in place with one side facing us. Our lunar companion rotates while it orbits Earth. It’s just that the amount of time it takes the moon to complete a revolution on its axis is the same it takes to circle our planet — about 27 days. As a result, the same lunar hemisphere always faces Earth.

How’d this come to be? In a word: gravity. The moon’s gravity slightly warps our planet’s shape and gives us tides. Likewise, Earth tugs at the moon, creating a rocky, high-tide “bulge” facing us. That bulge ended up working like a brake, slowing the moon’s spin down to the current rate, so the lunar high tide permanently faces us.

When that happened, about 4 billion years ago, the moon became “tidally locked,” and it has presented us the same visage ever since.

MIT Course 8.02 :Electricity and Magnetism( Study Material)

Course Highlights

This course features a complete set of videotaped lectures. The 36 video lectures on Electricity and Magnetism, by Professor Lewin, were recorded on the MIT campus during the Spring of 2002. Prof. Lewin is well-known at MIT and beyond for his dynamic and engaging lecture style.

Course Description
In addition to the basic concepts of Electromagnetism, a vast variety of interesting topics are covered in this course: Lightning, Pacemakers, Electric Shock Treatment, Electrocardiograms, Metal Detectors, Musical Instruments, Magnetic Levitation, Bullet Trains, Electric Motors, Radios, TV, Car Coils, Superconductivity, Aurora Borealis, Rainbows, Radio Telescopes, Interferometers, Particle Accelerators (a.k.a. Atom Smashers or Colliders), Mass Spectrometers, Red Sunsets, Blue Skies, Haloes around Sun and Moon, Color Perception, Doppler Effect, Big-Bang Cosmology.



Download

What is Elastic Potential Energy?

Elastic Potential Energy

Any object than can be deformed (have its shaped changed) and then return to its original shape can store elastic potential energy. • We’re still talking about potential energy, since it is stored energy until the object is allowed to
bounce back.
• “Elastic” does not refer to just things like elastic bands…other materials that would be referred
to as elastic would be
• pole vaulter’s pole
• springs

You learned in Physics that Hooke’s Law is…
F = kx
F = force (N)
k = spring constant for that object (N/m)
x = amount of expansion or compression (m)
We can use this formula to figure out a formula for the energy stored in the spring.
• Remember that W = F d

• We might be tempted to just shove the formula for Hooke’s Law into this formula to get
W = kxd = kx2
, but this is wrong!
• You have to take into account that the force is not constant as the object returns to its original
shape… it’s at a maximum when it is deformed the most, and is zero when the object is no…

If scientists can't see dark matter, how do they know it exists?

Q.If scientists can't see dark matter, how do they know it exists?

Ans. Scientists calculate the mass of large objects in space by studying their motion. Astronomers examining spiral galaxies in the 1950s expected to see material in the center moving faster than on the outer edges. Instead, they found the stars in both locations traveled at the same velocity, indicating the galaxies contained more mass than could be seen. Studies of the gas within elliptical galaxies also indicated a need for more mass than found in visible objects. Clusters of galaxies would fly apart if the only mass they contained were visible to conventional astronomical measurements.

Albert Einstein showed that massive objects in the universe bend and distort light, allowing them to be used as lenses. By studying how light is distorted by galaxy clusters, astronomers have been able to create a map of dark matter in the universe.

Although dark matter makes up most of the matter of the universe, it only makes …

What is the Physics Behind Vacuum Cleaner?

When you sip soda through a straw, you are utilizing the simplest of all suction mechanisms. Sucking the soda up causes a pressure drop between the bottom of the straw and the top of the straw. With greater fluid pressure at the bottom than the top, the soda is pushed up to your mouth. ­
This is the same basic mechanism at work in a vacuum cleaner, though the execution is a bit more complicated. In this article, we'll look inside a vacuum cleaner to find out how it puts suction to work when cleaning up the dust and debris in your house. As we'll see, the standard vacuum cleaner design is exceedingly simple, but it relies on a host of physical principles to clean effectively.

It may look like a complicated machine, but the conventional vacuum cleaner is actually made up of only six essential components:

An intake port, which may include a variety of cleaning accessories
An exhaust port
An electric motor
A fan
A porous bag
A housing that contains all the other components

When y…

Kaniz e zehra asked What is Heat?

11/13/2014 10:06:13 Kaniz e zehra asked What is Heat?

Consider a very hot mug of coffee on the countertop of your kitchen. For discussion purposes, we will say that the cup of coffee has a temperature of 80°C and that the surroundings (countertop, air in the kitchen, etc.) has a temperature of 26°C. What do you suppose will happen in this situation? I suspect that you know that the cup of coffee will gradually cool down over time. At 80°C, you wouldn't dare drink the coffee. Even the coffee mug will likely be too hot to touch. But over time, both the coffee mug and the coffee will cool down. Soon it will be at a drinkable temperature. And if you resist the temptation to drink the coffee, it will eventually reach room temperature. The coffee cools from 80°C to about 26°C. So what is happening over the course of time to cause the coffee to cool down? The answer to this question can be both macroscopic and particulate in nature.

On the macroscopic level, we would say that the coffee…

Kaniz e zehra asked Two unlike capacitor is charged to a certain potential difference it is then immersed in oil what happen to it s capacitance ,charge and potential?

11/13/2014 9:49:27Kaniz e zehra asked Two unlike capacitor is charged to a certain potential difference it is then immersed in oil what happen to it s capacitance ,charge and potential?

Ans.If you mean that an air capacitor is charged to a certain potential difference it is then immersed in oil what happen to it’s a)charge b)Potential and c) capacitance
Then the answer is :The dielectric constant Єr of the oil is grater than that of air.Whan an air capacitor is immersed in oil then
a)Its charge remain constant b)PD b/w the plates decreases c)the Capacitance increase.

But if the questions inlove two capacitors then the question will be same what like :Two unlike capacitors of different potentials and charges are joined in parallel.what happens to their pD?How are their charges distributed ?Is the energy of system affected? then answer will be :i)The potential difference will remain same.(ii) The charge is distributed (iii)The energy of the system decrease