Inertia Around a Curve
{Force and Motion
Inertia
• What is inertia?
• Inertia is the resistance an object has to
change in its state of motion.
• Who was the first to propose the concept of
inertia?
– Galileo Galilei
Galileo
• How do you think you could test the concept
of inertia?
• Did you know….
– Galileo developed the concept of inertia though a
series of experiments?
– Galileo was the first scientist to realize that
moving objects eventually stop because of friction
Galileo
• Galileo used a pair of inclined planes facing
each other. He noticed that if a ball rolled
down one plane and up the opposite at almost
the same height.
• If the planes where even smoother, the ball
would roll up the opposite side even closer to
the original height.
Galileo Concluded
• He reasoned that any difference between initial
and final heights was due to the presence of
friction between the ball and the plane.
• As a result, he concluded that if
all friction could be removed,
then the ball would reach exactly
the same height.
• He also realized that no mater
the angle of the planes, the balls
height on the uphill climb would
reach almost the same height.
Newton and Galileo
• Why not use what others have already discovered?
• Did you know that with Galileo’s discovery of the
concept of inertia, Newton used that information
and applied to his concepts of force?
• What do you think this resulted in?
• He decided that when the ball is rolling
indefinitely at constant speed and direction
(moving due to inertia), there is no acceleration or
force acting on the ball.
Moving
• What is “moving”?
– Moving is any change in position
– A change in motion is any change in speed,
direction or acceleration.
– An object traveling in a straight line at a
constant speed is moving (not accelerating).
• Why is it not accelerating?
–Because speed and direction is not
changing.
Activity
• You will investigate inertia by making
observations of a marble’s motion around a
circular track.
• You will predict and then observe the direction
the marble rolls when a section of the track is
removed and the marble moves due to its
inertia.
• You will also investigate whether changing the
mass of the marble affect the motion of the
marble.
Note
• This activity will depend on you observational
skills and your ability to describe what happens
in the investigation. THIS IS VERY
IMPORTANT for accurate results that you are
extra observant and detailed in your descriptions.
• Make sure you follow the directions carefully!
• Orient yourself so that the ball is not rolling
everywhere!