Motion of Objects

1
Motion of Objects

• Motion, Speed, and Velocity

2
Vocabulary for Motion

• motion acceleration negative acceleration
• speed momentum positive acceleration
• velocity reference point instantaneous speed
• distance average speed
• displacement

3
Motion

• motion is any change in location
• In order to tell if the location has changed, you
  must use a reference point - a location that is
  chosen to represent motion
• When something is moving relative to a reference
  point, its position relative to the reference
  point is changing. You can always choose a
  reference point depending on the motion of the
  object you want to describe.
• cars
• clouds
• See pg. 303 and Lets Demonstrate!

4
Distance and Time

• Time is the amount of period an object can take.
  
• Distance is the length of the path between two
  points.
• To be able to calculate the distance of two
  objects, we need to think of the displacement
  between them.
• Displacement refers to the difference between
  two points. If an object make a complete circle
  there is no displacement because they have ended
  in the same place that they started. However, if
  an object travels in a straight line, the total
  distance traveled would then be its displacement.

5
Motion and SI Unit of Measurement

• To describe motion completely, we must be able to
  measure using the International System of Units

Common Uses of SI Units Common Uses of SI Units
Distance meters (m)
Mass grams (g)
Time seconds (s) hours (h) minutes (min.) Days (d)
Liquid capacity liters (l)
6
Motion and SI (cont.)

• International System of Units Conversions
• K ilo (1,000)
• H ecto (100)
• D eka (10)
• D eci (0.1)
• C enti (0.01)
• M illi (0.001)

meter measures distance liter measures
liquid capacity grams - measures mass and weight
(1) m,l,g
7
Lets put SI to practice(distance)

• 5 cm _________ mm _______ mm 5 KM
• 10 dc ________ HM _______ cm 2 DM
• 5 KM ________ mm _______ dm 3 HM
• 8 DM ________ dm _______ cm 8 KM

8
Speed and Velocity

• The speed of an object is the distance the object
  moves per unit of time, while velocity is the
  speed of an object and its direction of motion.
• In order to calculate the speed of an object we
  must use the following formula which calculates
  the distance traveled divided by the time it
  takes to travel that distance
• EX V d / t ,

Variable Description Measurement
v speed m/s meters per second
d distance meters
t time seconds
9
Calculating speed, distance, or time

• Remember, V D/T
• Lets Practice!
• If a bicycle travels a total distance of 12 m in
  4 s. What is its average speed?
• What is the average speed of a sprinter who runs
  100 m in 10 s?
• What if an airplane travels 1,350 km in 3 h, what
  is its average speed?
• Lets put our practice to work!

10
Calculating Velocity

• Remember, velocity is the speed of an object and
  its direction of motion.
• EX If you were walking N at a speed of 2m/s,
  your velocity would be 2 m/s N.
• EX2 If you are walking east at the same speed,
  your velocity would then be 2 m/s E.
• Your velocity can change weather you change your
  speed or your direction!!
• Lets Practice on pg. 311!

11
Additional Voc. Review

• momentum - the product of the mass (always in an
  SI unit) and velocity of an object (p  mv)
• Calculate the momentum of a 11.35kg wagon
  rolling down a hill at 2 km/h
• constant speed speed that does not change and
  stays at the rate

12
Graphing Motion

• You can show the motion of an object on a line
  graph by plotting distance versus time.
• Graphing the motion of an object allows you to
  interpret the slope so that you can see how fast
  one variable changes in relation to the other
  variables in the graph.
• In order to calculate a slope you must follow the
  following formula
• Slope Rise/Run

13
Graphing Practice (see pgs. 312-313)
14
Acceleration

• Acceleration is any change in velocity.
  Therefore, if either speed or direction changes,
  so does the acceleration of the object. See pg.
  315 pictures as examples
• Formula
• Change in velocity (Vf Vi)
• _________________
• Time
• Lets Practice! pgs. 316 and 317

15
Additional Vocabulary Review

• Remember, acceleration is any change in velocity,
  that means an object is either increasing speed,
  decreasing speed, or changing direction.
• Keeping this in mind, we must understand then,
  that positive acceleration can be any change in
  direction but with increasing velocity (speed is
  increasing).
• On the other hand, negative acceleration is the
  opposite as it refers to either a negative change
  in direction with a decreasing velocity (speed is
  decreasing).

16
Graphing Acceleration (see pgs. 318-319)You can
use both a speed-versus-time graph and a
distance-versus-time graph to analyze the motion
of an accelerating object.