CSET Practice Test Subtest II Science

KINEMATICS 
"Kinematics is the branch of Physics in which we 
discuss bodies at rest or motion
without the reference of external agent that 
causes motion or rest." 
OR
"The branch of physics which deals with the 
description of motion of objects without
reference to the force or agent causing motion 
in it, is called Kinematics." 
REST 
"If a body does not change its position with 
respect to its surroundings then
the body is said to be in a state of rest." 
MOTION 
"If a body continuously changes its position with 
respect to its surrounding
than it is said to be in a state of motion." 
TYPES OF MOTION Motion of objects can be 
divided into three categories. (i) TRANSLATIONAL MOTION
(ii) ROTATIONAL MOTION
(iii) VIBRATIONAL MOTION

TRANSLATIONAL MOTION 
"Motion of a body in which every particle of the body 
is being displaced by the same amount is called 
Translational Motion". EXAMPLE: 
(i) Motion of a person on a road.
(ii) Motion of a car or truck on a road. 
ROTATIONAL MOTION 
"Type of motion in which a body rotates around a 
fixed point or axis is called Rotational Motion." 
EXAMPLE: 
(i) Motion of wheel
(ii) Motion of the blades of a fan 
VIBRATIONAL MOTION 
"Type of motion in which a body or particle moves to 
and fro about a fixed point or mean position is called 
Vibratory Motion." EXAMPLE:
(i) Motion of simple pendulum
(ii) Motion of the wires of guitar
(iii) Motion of swing 
DISPLACEMENT 
"Distance between two points in a particular direction 
is called Displacement." 
OR 
Displacement may also be defined as "the minimum 
distance between two points in a particular direction." 
It is a vector quantity and is always directed from the 
initial point to the terminal point. 
It is denoted by "d". 
SPEED 
"Distance covered by a moving body in one second is 
called its Speed".
OR
"Distance covered by a body in unit time is called Speed".
Speed is a scalar quantity. 
FORMULA 
Speed = Distance travelled/Time taken 
OR
v = S/t 
UNIT Unit of speed in S.I system is "m/sec". 
VELOCITY 
"Distance covered by a body in a particular direction in 
one second is called Velocity".
OR
"Displacement of a body in unit time is called Velocity".
OR
"Change of position of a body per second in a particular 
direction is called Velocity." 
FORMULA 
velocity = displacement/time 
UNIT In S.I system unit of velocity is meter/second. 
It is a vector quantity. 
ACCELERATION 
"The rate of change of velocity of a body is called 
Acceleration."
OR
"Change in velocity of a body in unit time is called its 
acceleration."
 It is denoted by "a".
It is a vector quantity. 
If a body moves with uniform velocity or constant 
velocity then its acceleration will be zero.
UNIT: m/sec2. 
FORMULA 
Acceleration = change in velocity/time
OR 
a = DV/t

Earth's Atmosphere

The present atmosphere of the Earth is probably not its 
original atmosphere. Our current atmosphere is what 
chemists would call an oxidizing atmosphere, while the 
original atmosphere was what chemists would call a 
reducing atmosphere. In particular, it probably did not 
contain oxygen. 

Composition of the Atmosphere
The original atmosphere may have been similar to the 
composition of the solar nebula and close to the 
present composition of the Gas Giant planets, though 
this depends on the details of how the planets 
condensed from the solar nebula. That atmosphere 
was lost to space, and replaced by compounds 
outgassed from the crust or (in some more recent 
theories) much of the atmosphere may have come 
instead from the impacts of comets and other 
planetesimals rich in volatile materials. 
The oxygen so characteristic of our atmosphere was 
almost all produced by plants (cyanobacteria or, more 
colloquially, blue-green algae). Thus, the present 
composition of the atmosphere is 79% nitrogen, 
20% oxygen, and 1% other gases. 

Layers of the Atmosphere

The Troposphere
The troposphere is where all weather takes place; it is 
the region of rising and falling packets of air. The air 
pressure at the top of the troposphere is only 10% of 
that at sea level (0.1 atmospheres). There is a thin 
buffer zone between the troposphere and the next layer 
called the tropopause. 

The Stratosphere and Ozone Layer
Above the troposphere is the stratosphere, where air 
flow is mostly horizontal. The thin ozone layer in the 
upper stratosphere has a high concentration of ozone, 
a particularly reactive form of oxygen. This layer is 
primarily responsible for absorbing the ultraviolet radiation 
from the Sun. The formation of this layer is a delicate 
matter, since only when oxygen is produced in the 
atmosphere can an ozone layer form and prevent an 
intense flux of ultraviolet radiation from reaching the 
surface, where it is quite hazardous to the evolution of 
life. There is considerable recent concern that manmade 
flourocarbon compounds may be depleting the ozone 
layer, with dire future consequences for life on the 
Earth.

The Mesosphere and Ionosphere
Above the stratosphere is the mesosphere and above 
that is the ionosphere (or thermosphere), where many 
atoms are ionized (have gained or lost electrons so 
they have a net electrical charge). The ionosphere is 
very thin, but it is where aurora take place, and is also 
responsible for absorbing the most energetic photons 
from the Sun, and for reflecting radio waves, thereby 
making long-distance radio communication possible.