Transcript chapter 2.3 understanding inertia

CHAPTER 2.3
UNDERSTANDING
INERTIA
LEARNING OUTCOME
By the end of the lesson, each
student should be able to:
1. Explain what inertia is
2. Relate mass to inertia
3. Give examples of situations involving
inertia
4. Suggest way to reduce negative effect of
inertia
LEARNING OUTCOME 1:
EXPLAIN WHAT INERTIA IS.
• Inertia is a property
of a body that tend to
maintain its original
state of motion
Inertia can be explain by
Newton’s first law of motion
“In the absence of
external force, an object
at rest will remain at rest
and object in motion will
remain its motion with
constant velocity in a
straight line”
State of motion
- Stationary
(object at rest)
-Moving with
constant
velocity
From Newton’s First Law,
an object at rest will remain at rest if
there are no external force acting on it
object in motion will remain its motion
with constant velocity in a straight line
unless there was external force acting
on it.
My superbike
will not stop
unless I apply a
force by pressing
the brake
LEARNING OUTCOME 2:
RELATE MASS TO INERTIA
The pail fill with
sand is more
difficult to push
compare to empty
pail.
A
B
When they start
swinging, the pail
fill with sand is
more difficult to
stop compare to
empty pail
• Which
person has
more mass,
the fat man
or the little
boy?
• Which one
has greater
inertia?
• Relate mass
and inertia
Learning Outcome 3: Give example
of situation involving inertia
When the cardboard is
pulled away quickly, the
coin drops straight into
the glass.
The inertia of the coin
maintains its state at
rest. The coin falls into
the glass due to gravity.
Chili sauce in the bottle
can be easily poured out
if the bottle is moved
down fast with a sudden
stop. The sauce inside the
bottle moves together
with the bottle. When the
bottle stops suddenly, the
sauce continue in its state
of motion due to the
effect of its inertia.
Body moves forward when the car stops suddenly
The driver were in a state of motion when the car
was moving. When the car stopped suddenly, the
inertia in the passengers made them maintain their
state of motion. Thus when the car stop, the
passengers moved forward.
LEARNING OUTCOME 4:
SUGGEST WAY TO REDUCE NEGATIVE EFFECT OF
INERTIA
Why we need to wear seat belt?
Furniture carried by a lorry normally are tied up
together by string. When the lorry starts to move
suddenly, the furniture are more difficult to fall off due
to their inertia because their combined mass has
increased.
Lets try some questions
1 Inertia of an object is
A
B
C
D
the friction force exerts to the object
the friction force exerts to the object
the force against the motion of the
object
the property of the object which
resists a change in its motion.
2 What is the name of the property of a body
which resists a change in its state of rest or of
uniform motion?
A
B
C
D
Inertia
Density
Velocity
Acceleration
3. Which object has the greatest inertia?
4 How difficult is it to start a heavy lorry moving
and to stop it moving ?
A
B
C
D
to move
difficult
difficult
easy
easy
to stop
difficult
easy
difficult
easy
Homework
• Please answer question in your Physics text
book
• Page : 32
• Discuss your answer with mentor/mantee.