• 8.1 The Language of Motion Pages 344 – 361 (c) McGraw Hill Ryerson 2007 8.1 The Language of Motion • Some common words used to describe motion include: Distance Time Speed •How would you describe the motion of the soccer Position ball before and after it is kicked? •What key words did you use when describing this situation? (c) McGraw Hill Ryerson 2007 Direction Makes a Difference • Two main types of quantities: Scalars: Describe magnitude but not direction. (Magnitude is the size of a measurement) Example: Johnny walked 25 km Vectors: Describe magnitude and direction. Example: Johnny walked 25 km North Every time you use a map or give directions, you are using vectors. (c) McGraw Hill Ryerson 2007 Vectors vs Scalars • You can always tell if a quantity is a vector because there will be an arrow drawn above it. Example: v 5.0m / s North • A scalar has no arrow. Example: v 5.0m / s (c) McGraw Hill Ryerson 2007 Distance and Displacement • Distance (d) is a scalar that tells you how far something has travelled. Example: Johnny ran a distance of 400 m • Displacement ( d ) is a vector that describes your position relative to where you started. Example: Johnny ran 400 m North of his home. • We measure both distance and displacement in metres (m). (c) McGraw Hill Ryerson 2007 Example A car leaves home and drives 10 km to the store and then returns home. The car has driven a total distance of 20 km but its final displacement is 0 km. Grover can teach us the difference too! (c) McGraw Hill Ryerson 2007 Time Interval • Time interval or change in time is calculated by: t t f ti Where: Δt = change in time (the Δ symbol is the greek letter delta. It means “change”. ti = initial time tf = final time (c) McGraw Hill Ryerson 2007 The time interval to move from the fire hydrant to the sign is calculated by: t 5 s 2 s 3 s (c) McGraw Hill Ryerson 2007 Displacement • Displacement or change in position is calculated by: d = df - di Where: d = change in position or displacement d i = initial position df = final position (c) McGraw Hill Ryerson 2007 Displacement and Distance Between 2 s and 5 s, the skateboarder’s: displacement is 5 m [E]. distance travelled is 5 m. (c) McGraw Hill Ryerson 2007 Watch for Signs Turn to page 349 for common sign conventions Copy Figure 8.8 into notes Turn to page 352 in textbook and do Activity 8-1B (c) McGraw Hill Ryerson 2007 Uniform Motion • Uniform motion is a term that describes objects that do not speed up, slow down, or change direction. • In other words, they travel at constant velocities (we will discuss velocity more later) (c) McGraw Hill Ryerson 2007 Uniform Motion Example The position of the ball in this photo is shown at equal time intervals. How would you determine if this motion is uniform motion? What would the picture look like if the ball was NOT in uniform motion? (c) McGraw Hill Ryerson 2007 Graphing Uniform Motion • Motion of an object can be analyzed by drawing a positiontime graph. • A position-time graph plots position data on the vertical axis (y-axis) and time data on the horizontal axis (x-axis). (c) McGraw Hill Ryerson 2007 • Uniform motion is represented by a straight line on a position-time graph. (c) McGraw Hill Ryerson 2007 Positive Slope • Positive slope Slants up to the right. Indicates an object travelling in the positive direction (ie: North, East, to the right, up, etc.) (c) McGraw Hill Ryerson 2007 Zero Slope • Zero slope Horizontal line. Indicates that the object is stationary. (c) McGraw Hill Ryerson 2007 Negative Slope • Negative slope Slants down to the right. • Indicates an object travelling in the negative direction (ie: South, West, to the left, down, etc.) (c) McGraw Hill Ryerson 2007 Homework • Complete questions 1 – 17 on page 361 in full sentences. • Expect a short quiz at the beginning of next class. (c) McGraw Hill Ryerson 2007

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# 1.1 Safety in the Science Classroom