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Describing Motion

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Describing Motion Section 2.1 SC Standards Covered PS-5.1 Explain the relationship among distance, time, direction, and the velocity of an object PS 5.2 Use the ... – PowerPoint PPT presentation

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Title: Describing Motion


1
Describing Motion
  • Section 2.1

2
SC Standards Covered
  • PS-5.1 Explain the relationship among distance,
    time, direction, and the velocity of an object
  • PS 5.2 Use the formula vd/t to solve problems
    related to average speed or velocity
  • PS 5.6 Represent linear motion of objects on
    distance time graphs

3
Motion
  • Motion when an object changes its position
  • Reference point- an indicator that orients
    you---the place from which you measure, record,
    or witness an event
  • Distance how far an object has moved
  • -measured in meters (m)
  • Displacement distance and direction of an
    objects change of position from a starting point
    (see pg. 38-39 in text)

4
Displacement
5
Pythagorean Theorem
  • Displacement
  • a2 b2 c2
  • Example Joe walks 4m North turns and walks 3m
    west. What is Joes distance and displacement?

6
Speed
  • Speed the distance an object travels per unit
    time
  • Speed distance d
  • time t
  • Units will always be some distance measurement
    divided by some time measurement

7
Types of Speeds
  • Average speed total distance traveled divided
    by total time traveled
  • Instantaneous speed speed at a given point in
    time.
  • This is what is shown on a speedometer

8
Calculating Speed
  • Example 1
  • Suppose you ran 2 km in 10 min. What is your
    speed?
  • s d
  • t
  • 2 km
  • 10 min.
  • 0.2km/min.

9
  • Example 2
  • Sound travels at 330 m/s. If a lightning bolt
    strikes the ground 2 km away from you, how long
    will it take for the sound to reach you?
  • 2km 2000 m
  • s d
  • t
  • 330 m/s 2000m
  • t
  • (330)(t) 2000
  • (330)(t) 2000
  • 330 330
  • t 6.06 s

10
You Try ?
  • A passenger elevator travels from the first floor
    to the 60th floor, a distance of 210 m, in 35 s.
    What is the elevators speed?
  • A motorcycle is moving at a constant speed of 40
    km/hr. How long does it take the motorcycle to
    travel a distance of 10 km?
  • How far does a car travel in 0.75 hr if it is
    moving at a constant speed of 88 km/hr?

11
Velocity
  • Velocity speed of an object and the direction
    of its motion
  • Speed can remain constant but if the direction of
    the object changes its velocity is changing
  • Calculated the same as speed

12
Vector vs. Scalar
  • Scalar- magnitude only
  • Example distance or speed
  • Vector- magnitude and direction
  • Example displacement or velocity

13
Graphing Motion
  • Graph distance on the y-axis and time on the
    x-axis
  • Slope rise distance speed
  • run time

14
Your turn!
  • Suppose a bus is traveling along a highway. It
    travels 100 km in the first 2 hrs and 120 km in
    the second 2 hrs. It stops for one hour, then it
    finishes the trip by going 100 km in two hours.
    Draw a distance verses time graph of the buss
    motion.
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