This document defines and explains key concepts related to motion and forces, including: - Position locates an object within a frame of reference and is represented by a vector. - Trajectory marks the position of an object over time within a reference frame and forms the path or line that connects each position. - Distance is the total length of the path or trajectory traveled by an object. Displacement is the distance and direction between an object's initial and final positions and is also represented by a vector. - Speed describes how fast an object is moving and is calculated as the distance traveled divided by the time taken to travel that distance. In the International System of units, speed is measured in meters per second

1. UNIT 1:
MOTION AND
FORCES
An approach to…

2. VOCABULARY
O Motion
O Rest
O Position (P)
O Frame of reference (SR)
O Vector
O Arrow
O Path
O Distance (∆s)
O Inicial
O Final
O Displacement (∆r)
O Length
O Position-time graph
O Speed-time graph
O To equal
O To increase
O Value
O Linearly
O To speed up
O To slow down
O To curve upward
O To curve downward
O Round-about

3. From your own experience…
O 1. Look at the figure. How can you determine
that the dog has been in motion?
O 2. How would you describe the position of the
bicycle?
O 3. Propose three different reference points you
could use to describe where you are right now.

4. Some known definitions
O POSITION (r)
O Position locates an object within a frame of
reference. Position is a vector — it is
represented by an arrow drawn in a frame of
reference.

5. Some known definitions
O TRAJECTORY (“path”)
O Trajectory is the imaginary line which marks
the position of an object at each instant for
a determined reference system.

6. Some known definitions
O DISTANCE (s)
O Distance for a moving object is the length of the path
(trajectory) the object travels.
In the figure, the runner traveled a distance of 50 m plus 30 m, or 80 m.

7. Some known definitions
O ➔ DISPLACEMENT( )
O Displacement is the distance and direction
of an object’s final position from its initial
position. It is a vector.
The runner’s displacement is 20 m north.
∆𝑟

8. In summary…
∆r rf
ri
trajectory
∆s

9. Speed

10. speed
O To describe how fast something is moving, you
need to know how far it travels in a given
amount of time.
O Speed is the distance an object travels per unit
of time.
O In SI (International system) units, the unit of
speed is meters per second (m/s).
At
As
v 
time
distance
m

11. An ex. of speed
O Sometimes it is more convenient to express average
speed in units other than m/s, such as kilometers per
hour (km/h).
O Ex.: What is the average speed of a car that travels a
distance of 750 m in 25 s? Express the result in km/h.
DO

12. Position-Time & Speed-Time
Graphs

13. Position-Time & Speed-Time
Graphs

14. Position-Time & Speed-Time
Graphs

15. Position-Time & Speed-Time
Graphs

16. QUESTIONS
O Define position, displacement and trajectory
O Compare displacement and trajectory
O ¿How can you call rfinal-rinitial?
O Write the unit of the speed in the IS