Circular Motion Definitions
The key thing here is the picture in the middle of the board. We have a ball moving in a circle. If there were no forces acting, the ball would follow the paths shown: constant velocity straight lines. So that it is moving in a circle means that there must be a force causing this. Three positions are sketched to show that for the ball to fall away from its straightline path, there must be a force in the directions shown. As the picture strongly suggests, these forces have a pattern- they seem to point to the center of the circle. For an object to move in a circle, this will always be true.
The right side of the board shows two vocab terms: centripetal force and centrifugal force.
Centripetal force is by far the more important. It means the inward force that keeps an object moving in a circle. Note that I cross out the word the. The centripetal force is not a new force, it is merely one of the forces that we've already studied, gravity, tension, magnetism etc.
Centrifugal force doesn't really exist. It's the fictitious force that results from our being objects in motion that try and stay in motion. As our inertia wants to carry us in a straight line, we feel this if something forces us to move in a circle. The term isn't useless- this fictitious force feels very real and can be used for useful things, like in a centrifuge.
Circular Motion Definitions
The key thing here is the picture in the middle of the board. We have a ball moving in a circle. If there were no forces acting, the ball would follow the paths shown: constant velocity straight lines. So that it is moving in a circle means that there must be a force causing this. Three positions are sketched to show that for the ball to fall away from its straightline path, there must be a force in the directions shown. As the picture strongly suggests, these forces have a pattern- they seem to point to the center of the circle. For an object to move in a circle, this will always be true.
The right side of the board shows two vocab terms: centripetal force and centrifugal force.
Centripetal force is by far the more important. It means the inward force that keeps an object moving in a circle. Note that I cross out the word the. The centripetal force is not a new force, it is merely one of the forces that we've already studied, gravity, tension, magnetism etc.
Centrifugal force doesn't really exist. It's the fictitious force that results from our being objects in motion that try and stay in motion. As our inertia wants to carry us in a straight line, we feel this if something forces us to move in a circle. The term isn't useless- this fictitious force feels very real and can be used for useful things, like in a centrifuge.