Observing Motion

A.Motion is an object’s change in position relative to a reference point. 1.Displacement is the change in the position of an object (direction). A.Motion is an object’s change in position relative to a reference point. 1.Displacement is the change in the position of an object (direction).

Describing Motion 1.Choose a destination near your home, such as school, a particular store, or a friend’s house. Write out a set of directions describing how someone would get from your home to the location. 2.Draw a map illustrating the directions you wrote out in Step 1. 3.Was it easier to write out the description or to draw the map? Which method is easier to use to find the location? Explain your answers. 1.Choose a destination near your home, such as school, a particular store, or a friend’s house. Write out a set of directions describing how someone would get from your home to the location. 2.Draw a map illustrating the directions you wrote out in Step 1. 3.Was it easier to write out the description or to draw the map? Which method is easier to use to find the location? Explain your answers.

Predicting a. Sample answer: Frame of reference may mean the range of distances or area that you are considering in a problem. b. Frame of reference is a system of objects that are not moving with respect to one another. Frames of reference are important because they are needed to accurately describe motion. a. Sample answer: Frame of reference may mean the range of distances or area that you are considering in a problem. b. Frame of reference is a system of objects that are not moving with respect to one another. Frames of reference are important because they are needed to accurately describe motion.

a)Distance measures a path taken b)Displacement is the change of an object’s position c)Displacement must always indicate direction. a)Distance measures a path taken b)Displacement is the change of an object’s position c)Displacement must always indicate direction.

Distance: Displacement along a line

Distance-Time Graphs The distance traveled by an object in a period of time often is expressed using a line graph. A line graph visually conveys information using sets of data points.

Distance-Time Graphs 1. Copy the blank graph below on your paper. Complete the graph by plotting the given data points on the graph. Each set of data points represents (time, distance). Note that time is measured in seconds and distance is measured in meters. Connect the plotted points with a straight line. Data points: (0, 0), (2, 40), (4, 80), (6, 120), (8, 160), (10, 200) 2.Describe the motion shown on the graph. 1. Copy the blank graph below on your paper. Complete the graph by plotting the given data points on the graph. Each set of data points represents (time, distance). Note that time is measured in seconds and distance is measured in meters. Connect the plotted points with a straight line. Data points: (0, 0), (2, 40), (4, 80), (6, 120), (8, 160), (10, 200) 2.Describe the motion shown on the graph.

B. Speed & Velocity 1.Speed is the distance traveled divided by the time interval during which the motion occurred.  Speed describes how fast an object moves.  Speed measurements involve distance & time.  SI units are meters per second (m/s). 1.Speed is the distance traveled divided by the time interval during which the motion occurred.  Speed describes how fast an object moves.  Speed measurements involve distance & time.  SI units are meters per second (m/s).

Average Speed/Velocity  Distance divided by time  V = D/T  Distance divided by time  V = D/T

2.Velocity is the speed of an object in a particular direction. 1.Velocity describes both speed & direction. 2.Velocity is the speed of an object in a particular direction. 1.Velocity describes both speed & direction.

Section 11.2 / pg 332 a.Average speed is distance divided by time. c. Instantaneous speed is different from average speed. e.Velocity is not the same as speed.

b. I could use this to calculate various speeds, like the average speed at which I travel getting to school. d.You can’t use a single speedometer reading to determine how long a trip will take. f.This could be useful in giving directions or in describing the path that you take on a walk. b. I could use this to calculate various speeds, like the average speed at which I travel getting to school. d.You can’t use a single speedometer reading to determine how long a trip will take. f.This could be useful in giving directions or in describing the path that you take on a walk.

Practice  Metal stakes are sometimes placed in glaciers to help measure a glacier’s movement. For several days in 1936, Alaska’s Black Rapids glacier surged as swiftly as 89 meters per day down the valley. Find the glacier’s velocity in m/s.

List the Given & Unknown Values  Given - Time, t = 1 day Displacement (distance), d = 89 m down the valley  Unknown Velocity, v = ? (m/s and direction)  Given - Time, t = 1 day Displacement (distance), d = 89 m down the valley  Unknown Velocity, v = ? (m/s and direction)

Perform Any Necessary Conversions  To find the velocity in meters per second, the value for time must be in seconds: T = 1 day = 24 hrs. x 60min/1h x 60s/1min T = 86,400s = 8.46 x 10 4 s  To find the velocity in meters per second, the value for time must be in seconds: T = 1 day = 24 hrs. x 60min/1h x 60s/1min T = 86,400s = 8.46 x 10 4 s

Write the Equation for Speed  Speed = Displacement/time = d/t

Insert the Known Values & Solve  V = d/t = 89m/8.64x10 4 s v = 1.0x10 -3 m/s down the valley  V = d/t = 89m/8.64x10 4 s v = 1.0x10 -3 m/s down the valley

Speed-Time Graphs The speed an object travels in a period of time can be expressed on a graph. This type of graph can give useful information about the object’s motion. The speed an object travels in a period of time can be expressed on a graph. This type of graph can give useful information about the object’s motion.

1.Describe the speed of the object shown on the graph. 2.The slope of the line on a distance-time graph represents the change in distance (m) per the change in time (s). Thus, the slope of a distance-time graph gives speed (m/s). What information does the slope of a speed-time graph give you? 3.What is the slope of the line on the speed-time graph? 1.Describe the speed of the object shown on the graph. 2.The slope of the line on a distance-time graph represents the change in distance (m) per the change in time (s). Thus, the slope of a distance-time graph gives speed (m/s). What information does the slope of a speed-time graph give you? 3.What is the slope of the line on the speed-time graph?

a. speed (or direction)b.direction (or speed) c.m/s 2 a. speed (or direction)b.direction (or speed) c.m/s 2