DESCRIBING MOTION: Kinematics in One Dimension CHAPTER 2

KINEMATICS AND MECHANICS The study of the motion of objects, and the related concepts of force and energy is called mechanics. Mechanics is usually divided into two parts… – Kinematics, which is a description of how objects move. – Dynamics, which is a study of forces and why objects move the way they do.

Kinematics Movement without rotation is called translational motion. Movement with a second movement about an axis is called rotational motion.

Reference Frames Any measurement must be made from a frame of reference. When specifying the motion of two objects or an object and its frame of reference, it is important to not only give the speed, but also the direction. (velocity) In physics, we often draw a coordinate axis, (pg 20) to represent the relative motion of objects.

Vector and Scalar A vector quantity has both direction and magnitude. A scalar quantity is a measurement that has only magnitude.

Displacement Displacement is the change in position of an object. It is a vector quantity. Distance is how far an object moves. It is a scalar quantity.  x= x 2 –x 1

Average Velocity Average speed= distance/ time Average Velocity= avg. displacement/ time

Instantaneous Velocity  = lim  x/  t Instantaneous velocity is the velocity at a single point in time.

Acceleration Average acceleration is the change in velocity per unit of time.