REPRESENTING MOTION Chapter 2 2 1 Picturing Motion

REPRESENTING MOTION Chapter 2

2. 1 Picturing Motion � Position changes when object is in motion � Straight � line, arc, circle, back and forth … Focus on straight line

Motion Diagrams � Represents position of object at equal time distances . . � � Particle model shows object as a dot Distance between dots shows equal time distances

2. 2 Where and When? � � � Measurements define a coordinate system Position – separation between object and origin Connecting origin with object’s position using arrow � Shows distance from origin � Direction of motion in direction of arrow � Can you have a negative position? Distance?

Vectors and Scalars � Vectors – quantities that require both direction and magnitude � Examples � ? Scalar – quantities that require only magnitude � Temperature, � time, distance Says nothing about units

Vectors � Giving directions � Travel 3. 7 km east to get to the store � Travel 1. 5 km east to get from the store to work � How far from the origin? 3. 7 km east + 1. 5 km east = 5. 2 km east � Represent it with a picture � Resultant – vector that represents the sum of the other vectors � Points from tail of first vector to tip of second vector

Time Interval & Displacement � � Time interval (Dt) is the difference between 2 times Dt = tf – ti � Sometimes t 0 � is used Changes in position called Displacement (Dd) � Vector quantity Sometimes indicated with (+ or -) signs � Dd = d f – di Sometimes d 0 is used � No indication of path taken by object

Dt and Dd . . Direction? ? Starting position? ? . . .

2. 3 Position-Time Graphs Intersections? Horizontal line? Positive vs. Negative slope? � Tells the same story as the motion diagram � Includes information about direction and starting position � Instantaneous position � Specific position at specific time

2. 4 How Fast? � � Rate of change in position is Average Velocity Vector quantity Slope of positiontime graph Absolute value of slope is average speed

Velocity � � Velocity at a specific instant is instantaneous velocity Instantaneous velocity different than average velocity � Average velocity is entire displacement divided by entire time interval � Avg v = Dd/Dt �d = avg v*t + di

Lab � Chapter 2, pgs 48 -49 � With multiple buggies