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

• 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.

• He reasoned that any difference between initial and final heights was due to the presence of friction between the ball and the plane.

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!