Intro to Motion Uniform and Non-Uniform Motion Speed and Velocity

Framing Questions What is the difference between uniform motion and non-uniform motion? What are examples of each? What is the difference between speed and velocity? What are the formulas for speed and velocity?

Uniform Motion Uniform motion is movement in a straight line at a constant speed Ex: A cyclist traveling on a straight path at a speed of 10m/s. Ex: A cyclist traveling on a straight path at a speed of 10m/s. It is important to know how to figure out uniform motion because it is the basis for the rest of physics… but uniform motion rarely exists How many times do you see something going at precisely the same speed in a precisely straight line? How many times do you see something going at precisely the same speed in a precisely straight line? This being said, we will focus on uniform motion in grade 10 so you understand the basics

Non-Uniform Motion Any movement not in a straight line or not at a constant speed is called non-uniform motion Ex: A car traveling around a corner Ex: A car traveling around a corner Most enduring motions are non-uniform We will touch on one (acceleration), but you will continue with the rest in grade 11 physics. For now you must understand the difference between these concepts…. For now you must understand the difference between these concepts….

Exercise: Uniform or Non-Uniform? A steel ball is dropped from your raised had to the floor A car is traveling north at a constant speed for 2 hours A jogger is running around a circular track at a constant speed A car is traveling a steady 60km/h due west A leaf flutters to the ground A rocket is launched from the Earth towards the moon A motorcycle rider applies the brakes in order to come to a stop A ball at the end of a rope is whirled around a person’s head at a constant speed of 8.0m/s The world’s fastest women compete in the 100m dash at the Olympics A marble rolls in a straight path down the hallway Is there ever a time when a motion which is non-uniform overall, is uniform at some point?

Speed, in Speed describes how fast something is moving It is scalar, so we indicate: Magnitude Magnitude Not direction Not direction The standard unit for measuring speed is m/s

Speed, in Symbols: Speed = v Speed = v Instantaneous speed (speed at a specific instant in time) = v inst Instantaneous speed (speed at a specific instant in time) = v inst Average speed (average speed over a particular time interval) = v av Average speed (average speed over a particular time interval) = v avFormula: Speed = distance Speed = distance time time v = d v = d t Example: The cyclist reached a maximum speed of 12.0 m/s during the race.

Velocity, in Velocity describes the speed and direction of motion This means it describes how fast an object’s position is changing This means it describes how fast an object’s position is changing Velocity is a vector, so we describe: Magnitude Magnitude Direction Direction The standard unit for measuring velocity is m/s

Velocity, in Symbols: Velocity = v Velocity = v Initial velocity = v i Initial velocity = v i Final velocity = v f Final velocity = v f Instantaneous velocity (velocity at a specific instant in time) = v inst Instantaneous velocity (velocity at a specific instant in time) = v inst Average velocity (average velocity over a particular time interval) = v av Average velocity (average velocity over a particular time interval) = v avFormula: Velocity = displacement Velocity = displacement time time v = d v = d tExample: The aircraft was traveling at 535km/h, headed 45° north of west The aircraft was traveling at 535km/h, headed 45° north of west

Practice Problem An object traveling at a constant speed travels due west for 800m in 40s. What is the speed of the object? What is the speed of the object? What is the velocity of the object? What is the velocity of the object? v = d/tv = d/t = 800m/40s = 800m due west/40s = 800m/40s = 800m due west/40s = 20 m/s = 20 m/s due west = 20 m/s = 20 m/s due west Note: When the object goes in a straight line, the magnitude for speed and velocity will always be the same!