This document provides a lesson on motion, including the following key points: 1. It describes goals to define motion, reference points, distance vs displacement, and perform speed calculations. 2. Key terms are introduced like speed, distance, displacement, and equations for calculating speed using distance and time. 3. Graphing motion is discussed where time is plotted on the x-axis and distance on the y-axis, and slope represents speed.

1. Describing Motion
Chapter 2: section 1
Tuesday 9/26/13

2. 2 Goals for this lesson
1. Describe motion
2. Perform calculations to determine speed

3. Motion and Position
• A reference point is needed to determine the
position of an object
• Motion occurs when an object changes its
position relative to a reference point
– Ex: How do people in a car know they are moving?
– Ex: Throw a ball, how do you know it moved

4. Distance vs Displacement
• Distance - how far an object has moved
– meter (m)
– Ex: It takes 4 laps around a 400m track to make
approximately a 1 mile race. What is the total
distance in meters?
• Displacement – the distance and direction of
an object relative to the starting point
– Ex: a person walks 20 m North, turns walks
10 m West, and then 20 m South, What is
the displacement?

5. Speed
•
•
•
•
•
Speed = s
Distance = d
Time = t
Most common unit = meters per second (m/s)
speed=Total distance traveled ÷ total time
Distance
Speed
Time
• This picture will help with solving
problems mathematically without
knowing Algebra!!

6. Practice problems
1. A passenger elevator travels from the first
floor to the 60th floor, a distance of 210 m, in
35 sec. What is the elevator’s speed?
2. How far does a car travel in 0.75 hours if it is
moving at a constant speed of 88 km/hour?
3. A motorcycle is moving at a constant speed
of 40 km/h. How long does it take to travel
10 km?

7. Homework
Speed worksheet
Tomorrow – Motion detector lab

8. Monday 9/30/13
• Pick up – 9.30 Reinforcement section 1

9. Goals for the lesson
1. Define speed terms
2. Interpret a position time graph
3. Perform calculations to determine velocity

10. Opener for Monday 9/30/13
1. Describe how the skier’s
velocity changes during
the race.
2. Why does the skier’s
velocity increase as he
races downhill?
3. How does being in a tuck
position affect a skier’s
motion?

11. Speed Terms
• Constant speed – if you maintain the same
speed over a time interval
• Changing speed – speed up or slow down over
a time interval
• Average speed - describes the speed of
motion when speed is changing
• Instantaneous speed – the speed at a given
point in time

12. Graphing Motion
• Time is plotted on the x axis
• Distance traveled is plotted on the y axis
• Slope of a distance-time graph = velocity (speed)
– Steeper line = faster
– Horizontal line = not moving, no speed
• Connect the dots with a straight “best fit” line not
a dot-to-dot line
– Easier to extrapolate data in between points

13. Position (m)
Interpreting a graph
• When is the object stopped? How do you know?
• When is it moving the fastest? slowest? Explain

14. Velocity
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•
•
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Velocity symbol = v
Displacement = x
Time = t
Includes the speed of an object but also the
direction of its motion.
• displacement ÷ total time = velocity
Displacement
Velocity Time

15. Homework
• Reinforcement sec 1
• Quiz Wednesday
– speed and velocity calculations
– interpreting graphs
– describing motion