Transcript Formal Presentation PPT

Newton's First Law of Motion
Law of Inertia
Miha Lee
Newton's First Law of Motion
• Every object in a state of uniform
motion tends to remain in that state
of motion unless an unbalanced
force is applied to it.
• An object at rest
• An object in motion
An Object at Rest
An Object in Motion
• Galileo's thought experiment I
An Object in Motion
• Galileo's thought experiment II
Frictional force
• Friction is the force that acts on a moving
object to slow it down and bring it to stop.
• Question 1: Evaluate the following
assertion.
If there is no frictional force on the road,
cars can move without consumption of
energy by the Newton’s first law of motion.
So we can save energy.
An Object in Motion
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A dynamic cart with a brick on it.
Get it moving and stopped.
Tape the brick to the cart.
Get it moving and stopped again.
Seat belts protect us from being hurt
by keeping us tied to the vehicle.
An Object in Motion
Inertia
• The resistance an object has to a
change in its state of motion.
• Question 2: What does the
magnitude of inertial force depend
on?
• F = ma
m: inertial mass
Application to everyday life
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Opening a bottle
Removing dusts from cloths
Seat belts
Seismometer
Seat Belt
• Seat belts can
exert forces to
cause passengers
to slow down at
the same rate as
the vehicle.
• Question 3: How
does a seat belt
exert force on us?
The principle of retractors