Transcript Newton`s First Law of Motion

Newton’s First Law of Motion
Unit 2: Forces and Motion
Observation
• I place 3 washers on top of a toy car. I am going to
push the toy car into a book on the table.
• What will the motion of the toy car be when it
collides with the book?
• What will the motion of the washers be when the toy
car collides with the book?
Why?
• Why did the car stop moving?
• Why did the washers fall forward?
Newton’s First Law of Motion
• An object in motion stays in motion, an object
at rest stays at rest UNLESS acted on by an
UNBALANCED force.
• Objects with a constant velocity or no motion
have zero net (balanced) force acting on them.
– Example:
• Waking up in the morning
• Air hockey table
Inertia (In-ER-sha)
• Describes the resistance of an object to
change its motion.
– It is directly related to the objects mass
• Example: Two boxes are sitting at rest on the
floor. They want to remain at rest. Which box
will be easier to move?
a. 20 g
b. 200 g
Explain this:
• When you’re standing in the Metro train, and
it arrives at the next station by stopping very
quickly.
• Why does the train stop? (it was in motion)
• What happens to you?
• Why do you fall forward a little bit when the
train stops?
Explain this:
• When you’re standing in the Metro train, and it
arrives at the next station by stopping very quickly.
• Why does the train stop? (it was in motion)
– An unbalanced force acted upon the train (brakes)
• What happens to you?
– you fall forward as the train stops
• Why do you fall forward a little bit when the train
stops?
– Because you were in motion with the train and you stayed
in motion because there was no unbalanced force acting
on you.
What happens here?
• You are in the car cruising at 40m/s. The driver
hits the brakes suddenly.
• What is your initial motion when the brakes
are hit?
• What keeps you from continuing to move
forward? (you are a safe passenger)
What happens here?
• You are in the car cruising at 40m/s. The driver
hits the brakes suddenly.
• What is your initial motion when the brakes are
hit?
– You begin to fly forward in the car because you were
in motion and wanted to stay in motion.
• What keeps you from continuing to move
forward? (you are a safe passenger)
– You are stopped from moving forward because you
were acted upon by an unbalanced force, the seatbelt
Think-Write-Pair-Share
• In the next slide – I will ask you to describe what
is going on in the series of pictures.
• Think – think about how Newton’s First Law
describes what is going on in the picture
• Write – write down 1 sentence description of
each of the pictures
• Pair – Pair with the student sitting next to you
and discuss your answers/opinion
• Share – Share out with the class what you and
your partner came up with as your answers.
Final Test
• Describe what is happening in each of these pictures
A)
B)
C)
Inertia (in-ER-sha) Practice
Which object has a greater inertia? The car or
the person flying out of it? Why?
Which one will require a GREATER unbalanced
force to stop its motion? The car or the person
flying out?
Inertia (in-ER-sha) Practice
Which object has a greater inertia? The car or
the person flying out of it? Why?
The car because it has a greater mass.
Which one will require a SMALLER unbalanced
force to stop its motion? The car or the person
flying out?
The person because it has a smaller mass.
Homework:
• Review pages 345-351
• Page 351, #1-6
Have a nice day!