Saturday, 14 February 2015
Friday, 13 February 2015
FORM 4: 2.13 MEANINGS
ITEM
|
MEANING
|
DISTANCE
|
Distance
is the total path length travelled from one location to another.
|
DISPLACEMENT
|
Displacement
is the distance between two locations measured along the shortest path
connecting them, in a specified direction.
|
SPEED
|
Speed
is the rate of change of distance.
|
VELOCITY
|
Velocity
is the rate of change of displacement.
|
ACCELERATION
|
Acceleration
is the rate of change of velocity.
|
DECELERATION
|
Deceleration
is the rate of decrease in speed in a specified direction.
|
INERTIA
|
The
inertia of an object is the tendency of the object to remain at rest or, if
moving, to continue its uniform motion in a straight line.
|
NEWTON’S FIRST LAW
|
Newton’s
first law states that every object continues in its state of rest or of
uniform motion unless it is acted upon by an external force.
|
MOMENTUM
|
Momentum
is defined as the product of mass and velocity.
|
PRINCIPLE OF CONSERVATION OF MOMENTUM
|
Principle
of conservation of momentum states that in the absence of an external force,
the total momentum of a system remains unchanged.
|
BALANCED FORCE
|
When
the forces acting on an object are balanced, they cancel each other out; the
net force / resultant force is equal to zero.
|
NEWTON’S SECOND LAW OF MOTION
|
The
acceleration produced by a net force on an object is directly proportional to
the magnitude of the net force applied and is inversely proportional to the
mass of the object. The direction of the acceleration is the same as that of
the net force.
|
IMPULSE
|
Impulse
is defined as the product of impulsive force and time interval.
|
Impulse
is also equal to the change of momentum.
|
|
IMPULSIVE FORCE
|
The
large force that acts over a short period of time during collisions and
explosions is known as impulsive force.
|
Impulsive
force can be defined as the rate of change of momentum in a collision or
explosion.
|
|
FREE FALL
|
An
object is falling freely when it is falling under the force of gravity only
(free from the influence of other forces).
|
ACCELERATION DUE TO GRAVITY
|
Acceleration
due to gravity is the acceleration of object falling freely.
|
GRAVITATIONAL FIELD
|
Gravitational
field is a region around the earth in which an object experiences a force
towards the centre of the earth.
|
GRAVITATIONAL FIELD STRENGTH
|
The
gravitational field strength at a point is defined as the gravitational force
acting on a 1 kg mass placed at that point.
|
WEIGHT
|
The
weight of an object is defined as the gravitational force acting on the
object.
|
RESULTANT FORCE
|
A
resultant force is a single force that can represent the combined effect of
two or more forces in magnitude and direction.
|
WORK
|
Work
is defined as the product of the applied force and the displacement of an
object in the direction of the applied force.
|
KINETIC ENERGY
|
Kinetic
energy is the energy of an object due to its motion.
|
GRAVITATIONAL POTENTIAL ENERGY
|
Gravitational
potential energy is the energy of an object due to its higher position in the
gravitational field.
|
PRINCIPLE OF CONSERVATION OF ENERGY
|
The
principle of conservation of energy states that energy can be transferred
from one form to another, but it cannot be created or destroyed.
|
POWER
|
Power
is defined as the rate at which work is done.
|
EFFICIENCY
|
Efficiency
is defined as the percentage of the energy input that is transformed into
useful energy.
|
ELASTICITY
|
Elasticity
is the property of a material that enables it to return to its original shape
and size when the force that was acting on it is removed.
|
HOOKE’S LAW
|
Hooke’s
law states that the extension of a spring is directly proportional to the
applied force provided that the elastic limit is not exceeded.
|
ELASTIC LIMIT
|
The
elastic limit of a spring is defined as the maximum force that can be applied
to a spring such that the spring will be able to be restored to its original
length even though the force not longer acts on it.
|
ELASTIC POTENTIAL ENERGY
|
Elastic
potential energy is the energy stored in a spring when it is extended or
compressed.
|
EXPERIMENT: HOOKE'S LAW
Aim
The aim of
this experiment is to find out the relationship between force and extension of
a spring.
Procedure
Thursday, 12 February 2015
FORM 4: 2.12 UNDERSTANDING ELASTICITY
THE MEANING OF ELASTICITY
Elasticity is the property of a material that enables it to return to
its original shape and size when the force that was acting on it is removed.
The elasticity of solids is due to the strong intermolecular forces
between the molecules of the solid.
HOOKE’S LAW
Hooke’s law states that the extension of a spring is directly
proportional to the applied force provided that the elastic limit is not
exceeded.
The elastic limit of a
spring is defined as the maximum force that can be applied to a spring such
that the spring will be able to be restored to its original length even though
the force not longer acts on it.
ELASTIC POTENTIAL ENERGY
Elastic potential energy is the energy stored in a spring when it is
extended or compressed.
FACTORS THAT AFFECT ELASTICITY
1. Length of spring
Longer
spring is more elastic.
2. Diameter of spring
Larger
diameter is more elastic.
3. Diameter of spring wire
Smaller
diameter of spring wire is more elastic.
4. Types of materials
The
elasticity changes with the type of materials.
5. Arrangement of springs
System of
springs is more elastic if the springs are arranged in series.
APPLICATIONS OF ELASTICITY
Wednesday, 11 February 2015
FORM 4: 2.11 APPRECIATING THE IMPORTANCE OF MAXIMISING THE EFFICIENCY OF DEVICES
SANKEY DIAGRAM FOR ENERGY CONVERSIONS IN THE
OPERATION OF A CAR
1.
Energy resources in this world are limited.
2.
It is very important that a device makes the best
possible use of the input energy.
3.
We should always think of ways to maximize the
efficiency of devices to help conserve resources.
Tuesday, 10 February 2015
FORM 4: 2.10 UNDERSTANDING WORK, ENERGY, POWER AND EFFICIENCY
THE MEANING OF WORK
Work is defined as the product of the applied force and the displacement
of an object in the direction of the applied force.
W = F x s
W = work done
F = force
s = displacement in the direction of force
SI unit for
work = Joule (J)
WORK FOR OBJECT THAT DOES NOT MOVE IN THE
DIRECTION OF THE APPLIED FORCE
W = F s cosθ
No work is done when
1.
a force is applied but no displacement occurs.
2.
an object undergoes a displacement with no applied
force acting on it.
3.
the direction of motion is perpendicular to the
applied force.
ENERGY
When work is done, energy is transferred from one object to another.
The work done is equal to the amount of energy transferred.
SI unit for energy = Joule (J)
THE MEANING OF KINETIC ENERGY
Kinetic energy is the energy of an object due to its motion.
THE MEANING OF GRAVITATIONAL POTENTIAL ENERGY
Gravitational potential energy is the energy of an object due to its
higher position in the gravitational field.
PRINCIPLE OF CONSERVATION OF ENERGY
The principle of conservation of energy states that energy can be
transferred from one form to another, but it cannot be created or destroyed.
This means that the total amount of energy always remain the same.
THE MEANING OF POWER
Power is defined as the rate at which work is done.
SI unit of power = Watt (W).
THE MEANING OF EFFICIENCY
Efficiency is defined as
the percentage of the energy input that is transformed into useful energy.
Monday, 9 February 2015
FORM 4: 2.9 ANALYSING FORCES IN EQUILIBRIUM
THE MEANING OF RESULTANT FORCE
A resultant force is a single force that can represent the combined
effect of two or more forces in magnitude and direction.
Resultant force, F = F1
+ F2
TWO FORCES THAT ACT IN OPPOSITE DIRECTIONS
Resultant force, F = F1
- F2
TWO FORCES ACTING AT A POINT AT AN ANGLE TO
EACH OTHER
RESOLUTION OF FORCES
A force can be resolved into two perpendicular components.
Horizontal component of force, Fx = F cosθ
Vertical component of force, Fy = F sinθ
FORCES IN EQUILIBRIUM
R = W cosθ
F = W sinθ
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