Intro to Kinematics

Scalars and Vectors We will come across and use two different 'kinds' of measurements as we study physics: 1. Scalars 2. Vectors Because these two measurements have fundamental differences we must: a) be able to distinguish between them b) follow different rules when using them

Scalars Scalar measurements tell us only the magnitude of the quantity being measured - Scalars numbers tell us "how many"   ex) 5 m (distance, s) 10 s (time, Δt) 100 kmh-1 (speed, v) The symbols used to denote scalars are usually letters  scalars can be added, subtracted, multiplied, divided, etc. just as ‘regular’ numbers can be ('regular' numbers are scalars…)

Vectors Vector measurements tell us the magnitude of the quantity being measured and the direction over which it is be measured Vector numbers tell us "how many" and "where" ex) 5 m [left] (displacement, ) 100 kmh-1 [east] (velocity, )   The symbols used to denote vectors are usually letters with a small arrow above them  Vectors can be added, subtracted, divided, etc. but we must modify the process used according to the direction attached to the quantity You CAN'T treat vectors like 'regular' numbers! we will learn how to add vectors that exist in a single dimension in this course…

Intro to Kinematics before we can hope to understand the physics of the moving world, we need to define some important terms used in this branch of physics the branch of physics that deals with motion is called kinematics as it turns out, our universe behaves in a very predictable fashion it appears to obey some very simple rules that can be summarized in the form of mathematical equations before we can understand and use these rules, we need to be able to measure and define a few fundamental quantities:

Distance and Displacement these expressions will appear in a few of the kinematics equations we will be using Distance (s): a scalar quantity that measures the space an object moves through our three dimensional world is equal to the sum of the distances moved in any and all spatial dimensions/directions measured in SI base units called metres (m)

Displacement ( ): a vector quantity that measures the space an object moves through our three dimensional world is equal to the vector sum of the distances moved in any and all spatial dimensions/directions measures a change in position (ie: the distance between the starting point and the ending point) measured in SI base units called metres (m)

Example: An MMC student walks 200 m [E] to get to school. After school this same student walks 50 m [W] to get to work. What is the total distance this student walked? What is the displacement of the student?

Time (Δt) whenever objects move through spatial dimensions, they are also moving through the dimension of time unlike spatial dimensions, all physical objects can only move in one direction through time: forward! during our study of kinematics we will see that the kinematics equations require that objects moves through time this movement in the time dimension is represented as the as ‘change in time” or Δt in equations expressed in SI base units called seconds (s)

Speed and Velocity Speed (v): Velocity ( ): a scalar quantity that measures how far an object travels (distance) in a given time expressed in SI base units called metres per second (ms-1) Velocity ( ): a vector quantity that measures the displacement of an object in a given time

Different “kinds” of Speed/Velocity “Kind” of Speed “Kind” of Velocity Definition Initial speed/velocity of object Final speed/velocity of object Average speed/velocity of object Change in speed/velocity u v

Acceleration ( ) an object experiences an acceleration whenever it’s velocity changes acceleration is equivalent to the rate of change of velocity if an object’s speed remains constant (ie: doesn’t change) the object is NOT accelerating! expressed in base units called metres per second2 (ms-2) Convention: if velocity “increases”, object is said to accelerate if velocity “decrease”, object is said to decelerate