Work
Work is done when an object moves from one place to another
Work is
measured with the formula
Work =
Force x displacement
So
W = F x d
= N x m
= Joule
Work is
done when
— There is force which acts on the
object
— An object moves
— The motion of an object is in the
direction of force
Example
— Calculate the work done is pulling a
wooden block with a force of 20 N through a displacement of 1.5 m
Solution
Work done =
force x distance
= 20 N x 1.5 m
= 30 J
— Calculate the work done to lift a
load of 500 g onto the surface of the table, if height of table is 0.8 m
Solution
W = F x d
= (m x g) x d
= 0.5 kg x 10 N/kg x 0.8 m
= 4 J
Power
— Power is the rate of work done
— Power is measured in joules per
second ( j s-1 ) which is
also called as Watt (W)
— Power is measured with the formula :
— Power = Work /Time
P = W / t
Example
— A student of mass 50 kg climbing a
distance which is 10 meters high. The time taken to climb the staircase is 20
second.(1 kg = 10 N)
- Find the power while climbing
the staircase?
- To produce twice the power.
Find the time taken by the student
Solution
- Power = (500 N x 10 m)/ 20 s =
250 W
- Time taken = (500 N x 10 m )/
(2 x 250 W )
ENERGY
The
Definition of Energy
Energy is
the ability to conduct work. The unit of energy in SI is joule (J). The other
unit for energy is calorie (cal). The relation between joule and calories is as
follows.
1 calorie = 4.2 joule or
1 joule = 0.24 calorie
Forms
of Energy
- Heat energy
- Electric energy
- Sound energy
- Light energy
- Nuclear energy
The
use of energy in daily life
- Solar energy d. Geothermal Energy
- Wind energy e. Tidal energy
- Water energy f. Nuclear energy
ENERGY
resource
ž Non renewable
ž Renewable
›
Ocean
The form of energy exchange
Energy can be transformed into many forms, such
as :
ž Light to heat
ž Electric to light
ž Electric to heat
ž Electric to sound
ž Chemical to electric
The form of energy exchange
ž Energy can be transformed into many
forms, but the amount of energy is constant. There is no increasing or
decreasing.
ž Only the form of energy has changed,
not its amount.
KINETIC Energy
ž Kinetic energy is the energy in the
form of movement, such as:
›
The
running children
›
The
rock fall
›
The
running car
Variable that have
ž Kinetic energy depend on the mass
and velocity of the moving object
›
The
larger the mass, the larger its kinetic energy
›
The
thing move faster, its kinetic energy become larger
Formula of kinetic energy
ž We can write formula kinetic energy
KE = ½ m v2
›
KE
= kinetic energy (joule)
›
m=
mass of moving object (kg)
›
V
= velocity of moving object (m/s)
Unit of kinetic energy
ž Unit of kinetic energy in SI system
is:
›
Joule
›
Kg
m2/s2
›
N.m
›
Watt.
Second
ž Another unit is:
›
Kalori 1 Kalori = 4.2 joule
POTENTIAL Energy
ž Potential energy is the energy
stored
ž Its amount depend on
›
its
the position or condition of the object
– If its position so higher, its
potential energy is greater
›
Its
mass
– The higher its mass, its potential
energy is greater
Formula of gravitational potential energy
ž We can write formula gravitational
potential energy
PE = m g h
›
PE
= gravitational potential energy (joule)
›
m
= mass of object (kg)
›
h
= high (m)
Unit of potential energy
ž Unit of potential energy in SI
system is:
›
Joule
›
Kg
m2/s2
›
N.m
›
Watt.
Second
ž Another unit is:
›
Kalori
Conservation of Energy
ž The potential energy is changed from
kinetic energy continuously.
ž Potential and kinetic energy
together in form mechanical energy.
ž It is a sum of potential and kinetic
energy in a system
ž Formula of mechanical energy
Em = Ek + Ep
ž Em = mechanical energy
ž Ep = Potential energy
ž Ek = kinetic energy
ž Energy can be transformed in one
form to another, but its total energy is constant. In other word, energy is conserved.
ž That is called the law of energy
conservation
ž Em1 = Em2 = Em3= Constant
Theory of Atom
Atom
is the smallest part of element
1. Each elements consist a small particles
which is called atom
2. Atoms of each element have a same of
characteristic, size and mass
3. Compound is a substance that consist of more
than one atom.
4. Chemical reaction is not change the
characteristic of atom, but only change the composition only.
Rutherford Theory
“Mass of atom center in nucleus, which have a positive
charge”
Niels Bohr Theory
Atom have a central
nucleus made up of protons and neutrons.
And electrons move around the
nucleus.
THE INVENTOR
OF PARTICLE SUB ATOMIC
- J.J Thomson, 1897 -----> electron
- Ernest Rutherford, 1911
----> proton
- James Chadwick, 1932 ---->
neutron
Electron symbol ( e )
Proton symbol ( p )
Neutron symbol ( n )
Catatan : Massa adalah dalam satuan massa atom (sma)
Massa elektron sangat kecil, sehingga
massanya = 0 sma
WRITE THE
SYMBOL OF ATOM
X = Name of Atom/Chemical Symbol
A = Atomic Number
Z = Mass Number
Atomic Number shows the
number of protons or electrons in its atom.
Mass number shows the total number of protons plus neutrons in the
nucleus.
A molecule that is composed
of similar atoms.
A
molecule is composed of different atoms.
Molecule of Compound
Molecule
1. Element : - Monoatomic
Element ( He, S, Fe, Ca, dll)
- Diatomic Element (O2, N2, H2, dll)
- Poliatomic Element (O3, P4, dll)
2. Compound :
- Diatomic Compound (NaCl, HCl, KCl, HBr,
dll)
- Poliatomic
Compound (H2SO4, NaOH,C6H12O6)
Isotopes, isobar, dan Isoton
The atoms of an element are not all alike. Some have more neutrons than
others. These different versions of the element are called isotopes.
Lithium have two isotopes with mass number 6 and 7.
The symbol of Lithium :
Isotopes
Isotopes have different mass numbers but the same atomic
number.
Isobar
Isobar have different atomic
number but the same mass number.
Isoton
Isoton have different both
atomic number and mass number but the same amount of neutrons.
PRESSURE
Science
word
Pressure
Force
Area
Fluids
Archimedes principle
Flooding
Flying
Sinking
Pressure in solid
Pressure is defined as force acting
on unit area
If pressure (p), force (F), and area
(A), we can write the formula below
Fluids
Pressure in fluid is produced by
collisions between particles and the container.
The characteristics of liquid pressure
Pressure in liquid increase with
depth
Pressure at one depth equally in all
direction
A liquid finds its own level in a U
- tube
Pressure depend on the density of
liquid.
Formula of liquid pressure
For the information above, pressure
of liquid just depend on 2 variable :
— Depth (h),
that
have relation pressure ~ depth
— Density (r)
that
have relations pressure ~ density
Formula of liquid pressure
We can write formula :
p ~ r.h
or
p = r.g.h
which pressure (p), depth (h), density (r ), and gravitation (g)
Pascal’s
principle
Pressure applied to an enclosed
liquid is transmitted to every part of liquid, whatever the shape of liquid.
Aplication pascal’s principle
Pascal’s principle is applied in the
operation of machines that use fluids to multiply force as in hydraulic lift
Hydraulic system
In a hydraulic system fluid is
confined in two connecting chambers.
Each chambers has a piston that is
free to move.
Pressure is
transmitted throughout the fluid without change
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