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# Tag Archives: earth

## Will the mass of earth reduce due to extraction of fossil fuels?

Is it possible that the earth mass would be reducing due to extraction of fossil fuels?

If so, would it affect to its movement and position in solar system?

Answer:

There won’t be any considerable loss of mass. The amount of mass **irrecoverably** lost is negligibly small on its conversion to energy .

It’s just like arguing that constructing more and more buildings will increase the mass of earth. !! No such thing happens. There is only a rearrangement of matter and inter conversion of mass and energy.

## Magnetism of Earth – What’s the cause?

**Selwyn posted this Message:** I was recently showing my grandchildren the effect on a compass needle by the magnetic field surrounding a magnet placed in opposition to the earth’s magnetic field – Magnetism 1.01 no? Their mother then asked me how is it that the earth has a magnetic field. I confidently answered that it was due to the central molten iron core of the earth acting as a magnet, and of course as we learned in Magnetism 1.1 68 years ago on of the ways of creating a magnet is a) by striking it several blows with a hammer while holding it in alignment with the earth’s N/S axis or b) heating it. In both cases this allows the atoms to move more freely and align themselves similarly with the axis. But that started me thinking: We know that heating ANYTHING applies energy to the atoms/molecules and this then causes them to display greater and more violent movement within the body of the material. If these molecules are so agitated, how can this identical phenomenon allow the molecule/atoms of the earth’s core to “settle down quietly” into a N/S configuration and remain so?

## Answer:

The answer is not so simple. Nobody has actually drilled into the centre of earth. What we know is by analysing the seismic waves and the shockwaves.

The Earth’s magnetic field is believed to be generated by electric currents in the conductive material of its core, created by convection currents due to heat escaping from the core. However the process is complex, and computer models that reproduce some of its features have only been developed in the last few decades. (Wikipedia)

The Earth and most of the planets in the Solar System, as well as the Sun and other stars, all generate magnetic fields through the motion of highly conductive fluids. The Earth’s field originates in its core. This is a region of iron alloys extending to about 3400 km (the radius of the Earth is 6370 km). It is divided into a solid inner core, with a radius of 1220 km, and a liquid outer core. The motion of the liquid in the outer core is driven by heat flow from the inner core, which is about 6,000 K (5,730 °C; 10,340 °F), to the core-mantle boundary, which is about 3,800 K (3,530 °C; 6,380 °F). The pattern of flow is organized by the rotation of the Earth and the presence of the solid inner core.

The mechanism by which the Earth generates a magnetic field is known as a dynamo.

(Wikipedia)

## The Dynamo Effect

The simple question “how does the Earth get its magnetic field?” does __not__ have a simple answer. It does seem clear that the generation of the magnetic field is linked to the rotation of the earth, since Venus with a similar iron-core composition but a 243 Earth-day rotation period does not have a measurable magnetic field. It certainly seems plausible that it depends upon the rotation of the fluid metallic iron which makes up a large portion of the interior, and the rotating conductor model leads to the term “dynamo effect” or “geodynamo”, evoking the image of an electric generator.

Convection drives the outer-core fluid and it circulates relative to the earth. This means the electrically conducting material moves relative to the earth’s magnetic field. If it can obtain a charge by some interaction like friction between layers, an effective current loop could be produced. The magnetic field of a current loop could sustain the magnetic dipole type magnetic field of the earth. Large-scale computer models are approaching a realistic simulation of such a geodynamo.

Refer to **this Wikipedia Page** and **this Hyperphysics page** for more details

The **GeoMag** page is also very informative and useful(Natural Resources Canada)

## Projectile Motion – Numerical Problems (Assignment for KV Pattom Class XI students)

The students are requested to start solving these numerical problems. More questions will be added **till 8 pm on 13/09/2014.** There will be **more than 20 questions** in all. All students are expected to solve at least 20 numericals among these. The deadline form submission is 15/09/2014.

- A football player kick a ball at an angle of 37° to the horizontal with an initial speed of 15 m/s. Assuming that the ball travels in a vertical plane, calculate (i) the time at which the ball reaches the highest point. (ii) the maximum height reached by the ball (iii) the horizontal range of the projectile and (iv) the time for which the ball is in air.
- A body is projected with a velocity of 20 m/s in a direction making an angle 60° with the horizontal. CCalculate (i) position after 0.5 seconds and (ii) velocity after 0.5 seconds
- The maximum vertical height of a projectile is 10 m. If the magnitude of the initial velocity is 28 m/s, what is the direction of the initial velocity? (g=9.8 m/s
^{2 }) - A bullet fired from a gun with a velocity of 140 m/s strikes the ground at the same level as the gun at a distance of 1 km. Find the angle of inclination with the horizontal at which the bullet is fired. (g=9.8 m/s
^{2 }) - A bullet is fired at an angle of 15° with the horizontal and hits the ground 6 km away. Is it possible to hit a target 10 km away by adjusting the angle of projection assuming the initial speed to be the same?
- A cricketer can throw a ball to a maximum horizontal distance of 160 m. Calculate the maximum vertical height to which he can throw the ball. (g=10 m/s
^{2 }) - A football is kicked with 20 m/s at a projection angle of 45°. A receiver on the goal line 25 metres away in the direction of the kick runs the same instant to meet the ball. What must be his speed, if he is to catch the ball before it hits the ground?
- A bullet fired at an angle of 60° with the vertical hits the ground at a distance of 2 km. Calculate the distance at which the bullet will hit the ground when fired at an angle of 45°, assuming the speed to be the same.
- A person observes a bird on tree 39.6 m high and at a distance of 59.2m. With what velocity the person should shoot an arrow at an angle of 45° so that it may hit the bird?
- A ball is thrown from the top of a tower with an initial velocity of 10 m/s at an angle of 30° with the horizontal. If it hits the ground at a distance of 17.3 m from the base of the tower, calculate the height of the tower. (Given g =10 m/s
^{2 }) - Prove that the time of flight T and the horizontal range R of a projectile are connected by the equation gT
^{2}=2R tanθ, where θ is the angle of projection. - Show that the range of a projectile for two angles α and β is same if α+β=90°
- A body is projected with velocity of 40 m/s. After 2 s it crosses a vertical pole of height 20.4 m. Calculate the angle of projection and horizontal range.
- A plane is flying horizontally at a height of 1000 m with a velocity of 100 m/s when a bomb is released from it. Find (i) the time taken by it to reach the ground. (ii) the velocity with which the bomb hits the target and (iii) the distance of the target.
- From the top of a building 19.6 m high a ball is projected horizontally. After how long does it strike the ground? If the line joining the point of projection to the point where it hits the ground makes an angle of 45° with the horizontal, what is the initial velocity of the ball.
- A body is thrown horizontally from the top of a tower and strikes the ground after 2 seconds at an angle of 45° with the horizontal. Find the height of the tower and the speed with which the body was thrown. Take g =9.8 m/s
^{2 }) - A ball is projected horizontally from a tower with a velocity of 4 m/s. Find the velocity of the ball after 0.7 s. (Given g =10 m/s
^{2 }) - In between two hills of heights 100 m and 92 m respectively , there is a valley of breadth 16m. If a vehicle jumps from the first hill to the second, what must be the minimum horizontal velocity so that it may not fall into the valley? (Given g =10 m/s
^{2 }) - A mailbag is to be dropped into a post office from an aeroplane flying horizontally with a velocity of 270 km/h at a height of 176.4 m above the ground. How far must the aeroplane be from the post office at the time of dropping the bag so that the bag directly falls into the post office?
- An aeroplane is flying in a horizontal direction with a velocity of 600 km/h and at a height of 1960 m. When it is above a point A on ground an object is dropped from it. The object strike the ground at the point B. Find the distance AB.
- Two tall buildings are situated 200 m apart. With what speed must a ball be thrown horizontally from the window 540 m above the ground in one building so that it will enter a window 50 m above the ground in the other?

###### Related articles

## Gravity

We all know there is no such thing as zero gravity even at the very end of universe there is micro gravity according to formula for gravity…!

Means we are away from certain object so the gravity exist in vacuum so now my question is:-

Q- We all know that there is zero Gravity in center of earth core so if we place an object in center of earth the would Gravity formula apply on that object or that object is in complete Zero gravity…????

Asked Pratik Bhoir

Answer:

If we simply keep a body at the centre, it will remain there as it is attracted equally in all directions.

**GRAVITY**

## Magnetic field due to current

A spinning electron creates a magnetic field.But what about an electron inside a current carrying wire electron is spinning around its axis and revolving in loop,both simultaneously.So,what if both the situations contradict (both magnetic fields are in opposite direction ).net M.F. should be zero then. I mean what is the fate of electron in a current carrying wire with respect to its spin?

Asked Aakanksha

## Determine unknown frequency with the help of beats

Two frequencies sounded together produce 3 beats per second.If one of the frequencies is 400 vibrations per second,the other frequency will be?

Asked Tayyab Mynir

Answer:

There are two possibilities because the beat frequency is equal to the difference in frequencies of the two sounding bodies.

So, the unknown frequency can be either 397 Hz or 403 Hz. This can be verified by lagging/ loading one of the sounding bodies.

Read more at http://en.wikipedia.org/wiki/Beat_(acoustics)