Chapter 1
Be, Present and Have
In
physical book or other science books, most of verbs use be, present and have. read
the following texts and find out the verb be, present and the verb have which
are given in the bold words.
Momentum
In classical mechanics, linear momentum or
translational momentum (pl. momentum; SI unit kg m/s, or, equivalently, N s) is the product of the mass and velocity
of an object. For example, a heavy truck moving fast has a large momentum—it takes
a large and prolonged force to get the truck up to this speed, and it takes a large and prolonged force to
bring it to a stop afterwards. If the truck were lighter, or moving slower,
then it would have less momentum.
Like velocity, linear momentum is a vector quantity, possessing a
direction as well as a magnitude:
Linear momentum is also a conserved quantity, meaning that if a closed system is
not affected by external forces, its total linear momentum cannot change. In
classical mechanics, conservation of linear momentum is implied by Newton's
laws; but it also holds in special relativity (with a modified formula) and,
with appropriate definitions, a (generalized) linear momentum conservation law holds in electrodynamics, quantum
mechanics, quantum field theory, and general relativity.
Newtonian
mechanics
Momentum has
a direction as well as magnitude. Quantities that have both a magnitude and a direction are known as vector
quantities. Because momentum has a
direction, it can be used to predict the resulting direction of objects after
they collide, as well as their speeds. Below, the basic properties of momentum
are described in one dimension. The vector equations are almost identical to the scalar equation.
1.1 Be and
have in scientific statements
a. read reading tests show that the
verb has to agree with the subject
form of be
singular plural
it they I am
he is we are
she you
Example
·
We are important to realize that in
physics today
·
He is the
father of physics in Indonesia, his name is Johannes Surya
·
Kinetic energy is energy of motion
·
wavelength is the
distance from the top of one crest to the top of the next crest, or from the bottom
of one trough to the bottom of the next trough.
1.2 simple present
a. form of the present simple
singular plural
It they
He verb+
s we + verb
She you
I
Example
·
A wave changes direction when it reflects from
a surface
·
When you learn
about a new physical quantity, such as mass, you need to know what units
are used to measure it.
b. form of have
singular plural
He we
She has They Have
It
Example
·
Electromagnetic waves have wavelengths that range from
kilometers, for radio waves, to less than the diameter of an atom, for x rays
and gamma rays.
·
blue light has a larger frequency and shorter wavelength than red light.
Exercise 1.2 Rewrite the
sentences by putting is, are or present
simple in the main verbs
1.
Electric forces often observed between
objects that have been prepared by rubbing (or other surface interactions), for
instance when clothes rub against each other in the dryer
.
2.
scientists recently made the
surprising discovery that certain ceramics are superconductors at less extreme
temperature.
3.
The vector
equations almost identical to the scalar equation.
4.
a piccolo a high-pitched sound or
tone, and a tuba makes a low-pitched sound.
5.
Two cars with different masses each
the same kinetic energy.
6.
the number of rotations per minute (or
per second) not a conserved quantity
7.
The symbol _ indicates that angular
momentum a positive or negative sign to
represent the direction of rotation
8.
Force
the rate of transfer of momentum
1.3 spelling changes
a . verb
ending in ss, sh, ch ,x and o is formed by adding -es to the base.
They pass he passes
They push he pushes
They watch they watches
They mix he mixes
They go he goes
It wash it washes
b. verb
ending in y after a consonant change y to -i and add -es.
They hurry he hurries
They
magnify he
magnifies
They study he studies
It fly it
flies
c. verb
ending in y after the vowel follows the main rule add s
they obey it obeys
they say he says
they play he plays
1.4 statement requiring the present simple
a. the
present simple is used for regular action and regular process:
Example:
·
He studies physics six hours a week
b. it is
used for the general statement
Example:
·
The value acceleration of gravity is
10 m/ s 2
c. it is
used for factual statements and observations
Exmple :
·
The gravitation force of the object is
2 N
·
The value of
d. it can
be used in descriptions of experiments
Example
·
Heavy of an object in the air is
different when that object on the water ,but its mass is same.
·
The temperature rises until it reaches 100,but after that it remains
constant.
In the other words ,always use the present simple unless there are
good reasons for using another tense.
Exercise
1.4 rewrite this sentences putting the verbs in bleakest into the correct form.
1.
He (study) physics
2.
The current (pass) along the wire
3.
This metal (weight) 125 grams
4.
Sound (travel) at a speed of 333
meters a second.
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