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Wednesday, March 31, 2010

general science#12

Distribution of elements on the surface of the earth

Element
Distribution
Element
Distribution
Oxygen
49.85%
Silicon
26.03%
Aluminium
7.28%
Calcium
3.18%
Sodium
2.33%
Potassium
2.23%
Magnesium
2.11%
Hydrogen
0.97%
Titanium
0.41%
Chlorine
0.20%
Carbon
0.19%
Others
1.00%

Metals and their ores

Substance
Ore
Substance
Ore
Calcium
Limestone, marble, chalk
Mercury
Cinnabar
Copper
Copper pyrites, Cuprite
Potassium
Carnelite, Saltpetre
Cement
Limestone and clay
Sodium
Rock salt, Cryolite
Glass
Silica and lime stone
Thorium
Monozite
Iodine
Sea weeds
Titanium
Rutile, limenite
Iron
Hematite, Magnatite, Iron pyrites
Uranium
Pitchblende
Gold
Aurite
Silver
Argentite

Metals and their alloys

Alloy
Component
Brass
Copper, Zinc
Bronze
Copper, Tin, Zinc
Gun metal
Copper, Tin, Zinc
Duralmin
Aluminium, Copper,
Magnesium, Manganese
Solder
Aluminium, Lead, Tin
Pewter
Lead, Tin


Notes

Speed is the rate of change of distance
speed = \frac{distance}{time}
Velocity is the rate of change of displacement. It signifies both the speed and the direction of movement of an object.
velocity = \frac{displacement}{time}
Acceleration is the rate of change of velocity.
acceleration = \frac{velocity}{time}
Acceleration due to gravity is the acceleration experienced by an object as it falls freely towards the ground. It is constant throughout the surface of the earth.
 g= 9.8 \frac{m}{s^2}
Momentum is a measure of the quantity of motion possessed by a body.
momentum = mass * velocity
Equations of motion
Let an object be moving for time t at an acceleration a resulting in a displacement s. If the initial velocity of the object is u and the final velocity v, the following equations hold true
v=u + at
s = ut + \frac{at^2}{2}
v^2 - u^2 = 2as
Newton’s laws of motion
First law: A body continues in its state of rest or uniform motion unless compelled to change by an unbalanced force
Second law: A body of mass m under an acceleration a experiences a force F given by F = ma
Third law: Whenever a body A exerts a force F on another body B, the second body B exerts force -F on A.

Questions

  1. The universal law of motion was propounded by

    1. Kepler
    2. Galileo
    3. Newton
    4. Copernicus
  2. The gravitational force with which the Sun attracts the Earth is

    1. less than the force with which the Earth attracts the Sun
    2. the same as the force with which the Earth attracts the Sun
    3. more than the force with which the Earth attracts the Sun
    4. constant throughout the year
  3. The mass of a body is different from its weight.

    1. Mass is variable whereas the weight is constant
    2. Mass varies very little at different places whereas weight varies significantly
    3. Mass is constant but weight increases from the pole to the equator
    4. mass is a measure of quantity of matter whereas weight is a force
  4. The weight of a body is

    1. same everywhere on the surface of the earth
    2. maximum at the poles
    3. maximum at the equator
    4. more on hills than in plains
  5. If a body is taken from the Earth to the Moon,

    1. its mass will be different but weight will still be the same
    2. both mass and weight will be different
    3. mass will be the same but weight will be different
    4. mass and weight will both remain unchanged

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