1. Chapter 10
Section 1

2. What is Motion? 1
Matter and Motion
All matter in the universe is constantly in motion, from the revolution of Earth around the Sun to elections moving around the nucleus of an atom.

3. Changing Position 1 Something is in motion if it is changing position.
What is Motion? 1
Changing Position
Something is in motion if it is changing position.
It could be a fast-moving airplane, a leaf swirling in the wind, or water tricking from a hose.
When an object moves from one location to another, it is changing position.

4. What is Motion? 1
Changing Position
The runners sprint from the start line to the finish line.
Their positions change, so they are in motion.

5. What is Motion? 1
Relative Motion
An object changes position if it moves relative to a reference point.
Picture yourself competing in a 100-m dash.
You begin just behind the start line.
When you pass the finish line, you are 100 m from start line.

6. What is Motion? 1
Relative Motion
If the start line is your reference point, then your position has changed by 100 m relative to the start line, and motion has occurred.

7. Distance and Displacement
What is Motion? 1
Distance and Displacement
Displacement includes the distance between the starting and ending points and the direction in which you travel.
This figure shows the difference between distance and displacement.

8. What is Motion? 1
Speed
Speed is the distance traveled divided by the time taken to travel the distance.
Speed can be calculated from this equation:

9. What is Motion? 1
Speed
In SI units, distance is measured in m (meters) and time is measured in s (seconds).
As a result, the SI unit of speed is the m/s—the SI distance unit divided by the SI time unit.

10. What is Motion? 1
Average Speed
Average speed is found by dividing the total distance traveled by the time taken.
An object in motion can change speeds many times as it speeds up or slows down.

11. What is Motion? 1
Average Speed
The speed of an object at one instant of time is the object's instantaneous speed.
If it takes you 0.5 h to walk 2 km to the library, your average speed would be as follows:

12. What is Motion? 1
Average Speed
Average speed, instantaneous speed, and constant speed are illustrated here.

13. You can represent the motion of an object with a distance-time graph.
What is Motion? 1
Graphing Motion
You can represent the motion of an object with a distance-time graph.
For this type of graph, time is plotted on the horizontal axis, and distance is plotted on the vertical axis.
Click box to view movie.

14. Distance-Time Graphs and Speed
What is Motion? 1
Distance-Time Graphs and Speed
Look at the graph.
According to the graph, after 1 s student A traveled 1 m.
Student B, however, traveled only 0.5 m in the first second.

15. Distance-Time Graphs and Speed
What is Motion? 1
Distance-Time Graphs and Speed
So student A traveled faster than student B.
The line representing the motion of student A is steeper than the line for student B.

16. Distance-Time Graphs and Speed
What is Motion? 1
Distance-Time Graphs and Speed
A steeper line on the distance-time graph represents a greater speed.
A horizontal line on the distance-time graph means that no change in position occurs.

17. What is Motion? 1
Velocity
If you are hiking in the woods, you want to know not only your speed, but also the direction in which you are moving.

18. This is why a compass and a map are useful to hikers.
What is Motion? 1
Velocity
The velocity of an object is the speed of the object and direction of its motion.
This is why a compass and a map are useful to hikers.

19. What is Motion? 1
Velocity
Velocity has the same units as speed, but it also includes the direction of motion.
The velocity of an object can change if the object's speed changes, its direction of motion changes, or they both change.

20. Section Check 1
Question 1
To determine whether something has changed position, you need a _______.
A. compass
B. global positioning system
C. map
D. reference point

21. Section Check 1
Answer
The answer is D. If someone starts a car and drives it 100 meters from its parking spot, the parking spot can be used as a point of reference to show that the car moved.

22. Section Check 1
Question 2
Displacement includes your _______ and _______ as well as the _______ in which you have traveled.

23. Section Check 1
Answer
It includes your starting point, ending point, and direction in which you have traveled. It is possible to have traveled a great distance and still have a displacement of zero if you traveled in an enormous circle and ended right where you began.

24. Question 3 1 Speed equals distance divided by _______. A. force
Section Check 1
Question 3
Speed equals distance divided by _______.
A. force
B. mass
C. time
D. velocity

25. Section Check 1
Answer
The answer is C. The smaller the t value in s=d/t, the greater the speed.