Physics Chapter Kinematics and Dynamics

Kinematics of Uniform Circular Motion

• Uniform circular motion is motion in a circle of constant radius at constant speed.
• Instantaneous velocity is always tangent to the circular path.
• Velocity is constantly changing direction, so there is acceleration.
• Centripetal acceleration is direction towards the center of the circle.
• Centripetal acceleration is equal to the square of the speed divided by the radius of the circle.

Dynamics of Uniform Circular Motion

• For an object to be in uniform circular motion, there must be a net force acting on it.
• The net force must be inward, towards the center of the circle.
• This force is called the centripetal force.
• There is no centrifugal force pointing outward; the object tends to move in a straight line.
• The centripetal force must be sufficient to overcome the object's tendency to move in a straight line.
• If the centripetal force vanishes, the object flies off tangent to the circle.

Highway Curves, Banked and Unbanked

• Banking the curve can help keep cars from skidding by providing a component of the normal force that acts towards the center of the circle.
• There's a speed where the entire centripetal force is supplied by the horizontal component of the normal force.
• At this speed, no friction is needed to keep the car moving in a circle.