ICPE Motion Unit

1
ICPE Motion Unit

• Adapted from Conceptual Physical Science
• By Jim Barnaby

2
Introduction

• What means of motion has done more to change the
  way cities are built than any other?
• The elevator

3
Introduction

• Importance of Simplification  
• Motion is best understood if you neglect effects
  of air drag, effects of buoyancy, spin and shape
  of moving objects.
• Air resistance is negligible for heavy compact
  (dense) objects at moderate speeds.
• Air resistance is important for light objects
  (feather) or heavy objects at high speeds.

4
Motion

• Demo
• Motion
• Change in position over time

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Frame of reference

• Frame of reference
• Background or object used for comparison
• All movement is described according to a frame of
  reference.
• Volunteers/illustrations

6
Speed

• Speed
• rate at which an object moves.
•  
• Speed distance V d
• time t
• Units m/s km/hr

7
Speed Problems

• A skateboard travels 120 meters in 6 seconds.
  Find its speed.
• Mr. Purdy runs 15 km in 90 minutes. What was his
  speed?

8
D t problems

• Mr. Catlow drives 36 km/hr for 75 minutes. How
  far did he drive?
• Mr. Barnaby rides his bike 65 km at 31.5 km/hr.
  How long was he riding?

9
Average speed

• Average Speed
• Includes breaks and periods of slower or faster
  speed
• Average speed total distance
  total time

10
Average speed

• Therefore, total distance covered average speed
  time interval
•  
• Ex An airplane flies 750 km in 1.25 hours. It
  lands for a 2.5 hour layover. Then it flies 275
  km in 45 minutes. What was its average speed?

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Velocity

• Velocity
• Speed in a given direction
• A train travels 150 m/s from Denver to Kansas
  City.
• What is its speed?
• What is its velocity?
• What is its velocity west?

12
Combine velocity

• Combining velocities
• Velocities in same direction are added
  together
•  
• Use subtraction to combine velocities in opposite
  directions

13
Vectors

• Vector
•   Any quantity described by a magnitude and
  direction (represented by an arrow)
•  
• Magnitude of velocity vector is speed

14
Vector problems

• Ex An airplane flies east at 200 km/hr. There
  is a tail wind of 50 km/hr. Use vectors to
  determine the velocity of the plane.
• Add velocities in same direction or measure
  vectors and convert
• 200 km/hr 50 km/hr 250 km/hr east

15
Vector problems

• Ex An airplane flies east at 200 km/hr. There
  is a headwind of 100 km/hr. Use vectors to
  determine the velocity of the plane.
• Subtract (measure vectors) 200 km/hr - 100
  km/hr 100 km/hr east

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Resultant

• Students read appendix C p. 756-759
• Resultant
•   Algebraic sum of 2 or more vectors
•  
• Find resultant using the parallelogram rule
• Construct parallelogram with the 2 vectors as
  adjacent sides tails together.

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Resultant problems

• Ex A bird flies north at 60 km/hr. It hits an
  easterly crosswind of 100 km/hr. Use vectors to
  determine the new velocity of the bird.

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Resultant Problems

• Ex An airplane flies 200 km/hr south. It hits
  a westerly crosswind of 80 km/hr. What is the
  new velocity of the airplane.

19
Study guide fun

• Solve study guide problems 7, 11, 21, 34, 37, 38,
  39

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Acceleration

• There are 3 controls in an automobile that
  make a car accelerate. What are they?
•   Accelerator
• Brakes
• Steering Wheel
• Demos

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Acceleration

• Acceleration
•   Rate of change in velocity
•  
• Acceleration Final Velocity - Initial
  Velocity
• Time
•  A VF - VI
• T
•  
• Units Km/hr/s or m/s/s (m/s2)

22
Acceleration problems

• Find the acceleration of a car that goes from 30
  km/hr to 100 km/hr in 7 seconds.
• As Kailie performs another scorching serve, the
  tennis ball goes from rest to 140 km/hr in 1.8
  seconds. Find acceleration.

23
Acceleration problems

• Sierra is snowboarding 20 m/s at the bottom of a
  hill. Three seconds later she reaches the top of
  the next hill with a speed of 2 m/s. Find
  acceleration.
• Deceleration
• Negative acceleration (slowing down)

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Free Fall

• Free Fall
•   An object falls under the influence of only
  gravity - free from air resistance
•  Acceleration of gravity 9.8 m/s/s (9.8 m/s2)
•  

25
Free Fall

• Well use 10 m/s2
•  
• During each second of free fall, the object gains
  a speed of 10 m/s.
•  

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Free fall problems

• If an object is dropped from an initial position
  of rest from the top of a cliff, how fast is it
  moving after 1 second? 2 seconds?
•  
• Velocity acquired acceleration ? time
•  
• V g t g 10 m/s2
• Write chart on board/students fill out

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Terminal Velocity

• Terminal Velocity Object in free fall no longer
  accelerates (constant speed) as the force of air
  resistance balances the weight of the object.
  (depends on shape of object..) more on this
  in forces unit
• Read paragraph p. 13 in teachers manual speed
  skiers

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Upward Motion

• Upward Motion speed decreases at 10 m/s each
  second. (10 m/s2)
• Sketch picture on board

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Free fall distance

• Distance traveled ½ (acceleration time
  time)
•  For a freely falling object that starts from
  rest
• D ½ g t2 or d g t2
• 2
•  How far will a freely falling object released
  from rest, fall in 1 second? 2 seconds?
• Write chart on board, students fill out
• High throw contest outside

30
Free fall distance

• A climber near the summit of a vertical cliff on
  Mt. St. Waters (located in NW Montana) knocks
  loose a large rock. It hits the bottom 8 seconds
  later. What was the speed of the rock on impact?
  How far did the rock fall?

31
Acceleration

• Q Consider a rifle fired straight downward from a
  high altitude balloon. If muzzle velocity is 100
  m/s and air resistance is neglected. What is the
  acceleration of the bullet after 1 second?
• It is g 10 m/s2

32
Vectors/scalars

• Vectors - any quantity with direction and
  magnitude (velocity, force, momentum)
• Scalars - any quantity with magnitude only (no
  direction) (time, temperature, mass, energy .)

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Gravity experiment

• Design an experiment to determine the
  acceleration of gravity for various objects (You
  must use three different formulas to achieve your
  answer. Report the most correct answer on the
  board, brief presentation on why you believe that
  formula yielded the most accurate value for
  gravity) Turn this in for a grade!
• Each student does their own procedure, a group of
  4 will pick the best procedure and follow it to
  determine g. (staple all together)

34
T Vs. D T Vs. V Graphs

• Sketch T Vs. D and T Vs. V graphs
• Examples of graphs are on study guide

35
Graphs handout

• Complete graphing handout in groups of two
• Prepare for unit quiz