Chapter 2 Motion
2-1. Speed
2-2. Vectors
2-3. Acceleration
2-4. Distance, Time, and
Acceleration
2-5. Free Fall System
2-6...
2-1. Speed
• Definitions:
– Speed
• The rate at which something moves a given distance.
• Faster speeds = greater distance...
2-1. Speed
Velocity

miles
 d   100miles 
v= =
= 40mph
 = 40
hour
 t   2.5hours 
Distance

d = v ⋅ t = 30

( )...
2-1. Speed
Average speed is the total
distance traveled by an
object divided by the
time taken to travel that
distance.
In...
2-2. Vectors
Magnitude of a quantity
tells how large the
quantity is.
Scalar quantities have
magnitude only.
Vector quanti...
2-2. Vectors
Velocity is a vector quantity that includes both speed and
direction.
2-3. Acceleration
Acceleration of an object is the rate of change of its
velocity and is a vector quantity. For straight-l...
2-3. Acceleration
3 Types of Acceleartion
Speeding Up
Slowing Down
Turning
2- 4. Distance, Time and
Acceleration
Vavg =

(V1 + V2)

(20mph + 60mph)

2

2

= 40mph

d = vavg t

30mph 2hr = 60miles

...
2-5. Free Fall
The acceleration of
gravity (g) for objects
in free fall at the
earth's surface is 9.8
m/s2.
Galileo found ...
2-5. Free Fall
The rate of falling
increases by 9.8 m/s
every second.
Height = ½ gt2
For example:

½ (9.8 )12 = 4.9 m
½(9....
2-5. Free Fall
A ball thrown
horizontally
will fall at the
same rate as a
ball dropped
directly.
2-5. Free Fall
A ball thrown into the
air will slow down, stop,
and then begin to fall
with the acceleration
due to gravit...
2-5. Free Fall

An object thrown upward at an angle to
the ground follows a curved path called
a parabola.
2-6. Air Resistance
• In air…
– A stone falls faster
than a feather
• Air resistance
affects stone less

• In a vacuum
– A...
2-6. Air Resistance
• Free Fall
– A person in free
fall reaches a
terminal
velocity of
around 54 m/s
– With a
parachute,
t...
2-6. Air Resistance
• Ideal angle for a projectile
– In a vacuum, maximum distance is at an angle of 45o
– With air resist...
2-7. First Law of Motion
The first law of
motion states: If
no net force acts
on it, an object at
rest remains at
rest and...
Foucault Pendulum
Inertia keeps a pendulum
swinging in the same
direction regardless of the
motion of the earth. This
can ...
Foucault Pendulum
Other Web sites that illustrate the Foucault Pendulum.
http://en.wikipedia.org/wiki/File:Foucaultrotz.gi...
2-8. Mass
Inertia is the apparent resistance
an object offers to any change in
its state of rest or motion.
2-9. Second Law of Motion
Newton's second law
of motion states: The
net force on an object
equals the product of
the mass ...
2-9. Second Law of Motion
A force is any
influence that
can cause an
object to be
accelerated.
The pound (lb) is
the unit ...
2-10. Mass and Weight
• Weight
Definition: The force with which an object is
attracted by the earth’s gravitational pull
•...
2-11. Third Law of Motion
The third law of
motion states:
When one object
exerts a force on a
second object, the
second ob...
2-11. Third Law of Motion
Examples of the 3rd Law
2-12. Circular Motion
Centripetal force is the inward force exerted on an object
to keep it moving in a curved path.
Centr...
2-12. Circular Motion
2-12. Circular Motion
833 N is needed to make this turn.
If he goes too fast, which wheels are likely to
come off the grou...
2-13. Newton's Law of
Gravity
Gm1m2
Gravitational force = F =
R2

G = 6.67 x 10-11
N•m/kg2
2-13. Newton's Law of
Gravity
• How can we determine the
mass of the earth using an
apple?
– This illustrates the way
scie...
2-13. Newton's Law of
Gravity
• How can we determine the mass of the
earth using an apple?
– This illustrates the way scie...
2-15. Artificial Satellites
• The world's first artificial
satellite was Sputnik I, launched
in 1957 by the Soviet Union.
...
2-15. Artificial Satellites
The escape speed is the speed
required by an object to leave the
gravitational influence of an...
2-15. Artificial Satellites
The escape speed is the speed
required by an object to leave the
gravitational influence of an...
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C2 motion

  1. 1. Chapter 2 Motion 2-1. Speed 2-2. Vectors 2-3. Acceleration 2-4. Distance, Time, and Acceleration 2-5. Free Fall System 2-6. Air Resistance 2-7. First Law of Motion 2-8. Mass 2-9. Second Law of Motion 2-10. Mass and Weight 2-11. Third Law of Motion 2-12. Circular Motion 2-13. Newton's Law of Gravity 2-14. Artificial Satellites
  2. 2. 2-1. Speed • Definitions: – Speed • The rate at which something moves a given distance. • Faster speeds = greater distances – General formula for speed: • Speed = distance / time • Abbreviations commonly used: d = distance t = time v = speed v = d/t
  3. 3. 2-1. Speed Velocity miles  d   100miles  v= = = 40mph  = 40 hour  t   2.5hours  Distance d = v ⋅ t = 30 ( )⋅6 miles hour hours = 180miles Time miles  d   100miles  t = = = 2.5hours  = 2.5 miles / hour  v   40miles / hour 
  4. 4. 2-1. Speed Average speed is the total distance traveled by an object divided by the time taken to travel that distance. Instantaneous speed is an object's speed at a given instant of time.
  5. 5. 2-2. Vectors Magnitude of a quantity tells how large the quantity is. Scalar quantities have magnitude only. Vector quantities have both magnitude and direction.
  6. 6. 2-2. Vectors Velocity is a vector quantity that includes both speed and direction.
  7. 7. 2-3. Acceleration Acceleration of an object is the rate of change of its velocity and is a vector quantity. For straight-line motion, average acceleration is the rate of change of speed: change in speed Acceleration = time interval vf − vi a= t
  8. 8. 2-3. Acceleration 3 Types of Acceleartion Speeding Up Slowing Down Turning
  9. 9. 2- 4. Distance, Time and Acceleration Vavg = (V1 + V2) (20mph + 60mph) 2 2 = 40mph d = vavg t 30mph 2hr = 60miles d = ½at2 ½ 10m/s/s 52 = 125m
  10. 10. 2-5. Free Fall The acceleration of gravity (g) for objects in free fall at the earth's surface is 9.8 m/s2. Galileo found that all things fall at the same rate.
  11. 11. 2-5. Free Fall The rate of falling increases by 9.8 m/s every second. Height = ½ gt2 For example: ½ (9.8 )12 = 4.9 m ½(9.8)22 = 19.6 m ½ (9.8)32 = 44.1 m ½ (9.8)42 = 78.4 m
  12. 12. 2-5. Free Fall A ball thrown horizontally will fall at the same rate as a ball dropped directly.
  13. 13. 2-5. Free Fall A ball thrown into the air will slow down, stop, and then begin to fall with the acceleration due to gravity. When it passes the thrower, it will be traveling at the same rate at which it was thrown.
  14. 14. 2-5. Free Fall An object thrown upward at an angle to the ground follows a curved path called a parabola.
  15. 15. 2-6. Air Resistance • In air… – A stone falls faster than a feather • Air resistance affects stone less • In a vacuum – A stone and a feather will fall at the same speed.
  16. 16. 2-6. Air Resistance • Free Fall – A person in free fall reaches a terminal velocity of around 54 m/s – With a parachute, terminal velocity is only 6.3 m/s • Allows a safe landing
  17. 17. 2-6. Air Resistance • Ideal angle for a projectile – In a vacuum, maximum distance is at an angle of 45o – With air resistance (real world), angle is less • Baseball will go furthest hit at an angle of around 40 o
  18. 18. 2-7. First Law of Motion The first law of motion states: If no net force acts on it, an object at rest remains at rest and an object in motion remains in motion at a constant velocity.
  19. 19. Foucault Pendulum Inertia keeps a pendulum swinging in the same direction regardless of the motion of the earth. This can be used to measure the motion of the earth. As the Foucault Pendulum swings it appears to be rotating, but it is the earth that is rotating under it. To the right is the Foucault Pendulum at the Pantheon in Paris, France.
  20. 20. Foucault Pendulum Other Web sites that illustrate the Foucault Pendulum. http://en.wikipedia.org/wiki/File:Foucaultrotz.gif http://www.physclips.unsw.edu.au/jw/foucault_ pendulum.html http://aspire.cosmicray.org/labs/scientific_method/pendulum.swf http://www.calacademy.org/products/pendulum /page7.htm http://www.youtube.com/watch? v=nB2SXLYwKkM
  21. 21. 2-8. Mass Inertia is the apparent resistance an object offers to any change in its state of rest or motion.
  22. 22. 2-9. Second Law of Motion Newton's second law of motion states: The net force on an object equals the product of the mass and the acceleration of the object. The direction of the force is the same as that of the acceleration. F = Ma
  23. 23. 2-9. Second Law of Motion A force is any influence that can cause an object to be accelerated. The pound (lb) is the unit of force in the British system of measurement: 1 lb = 4.45 N (1 N = 0.225 lb) 1 newton = 1 N = 1 (kg)(m/s 2 )
  24. 24. 2-10. Mass and Weight • Weight Definition: The force with which an object is attracted by the earth’s gravitational pull • Example: A person weighing 160 lbs is being pulled towards the earth with a force of 160 lbs (712 N). – Near the earth’s surface, weight and mass are essentially the same Weight = (mass)(acceleration of gravity) w = mg
  25. 25. 2-11. Third Law of Motion The third law of motion states: When one object exerts a force on a second object, the second object exerts an equal force in the opposite direction on the first object.
  26. 26. 2-11. Third Law of Motion Examples of the 3rd Law
  27. 27. 2-12. Circular Motion Centripetal force is the inward force exerted on an object to keep it moving in a curved path. Centrifugal force is the outward force exerted on the object that makes it want to fly off into space.
  28. 28. 2-12. Circular Motion
  29. 29. 2-12. Circular Motion 833 N is needed to make this turn. If he goes too fast, which wheels are likely to come off the ground first?
  30. 30. 2-13. Newton's Law of Gravity Gm1m2 Gravitational force = F = R2 G = 6.67 x 10-11 N•m/kg2
  31. 31. 2-13. Newton's Law of Gravity • How can we determine the mass of the earth using an apple? – This illustrates the way scientists can use indirect methods to perform seemingly “impossible tasks”
  32. 32. 2-13. Newton's Law of Gravity • How can we determine the mass of the earth using an apple? – This illustrates the way scientists can use indirect methods to perform seemingly “impossible tasks”  GmM  = mg Gravitational force on apple = F =  ÷ R2    gR 2  (9.8m / s 2 )(6.4 ×106 m) 2 M = = = 6 × 1024 kg ÷ G  6.67 ×10−11 N ×m 2 / kg 2 
  33. 33. 2-15. Artificial Satellites • The world's first artificial satellite was Sputnik I, launched in 1957 by the Soviet Union. GPS-Global Positioning Satellite
  34. 34. 2-15. Artificial Satellites The escape speed is the speed required by an object to leave the gravitational influence of an astronomical body; for earth this speed is about 40,000 km/h.
  35. 35. 2-15. Artificial Satellites The escape speed is the speed required by an object to leave the gravitational influence of an astronomical body; for earth this speed is about 40,000 km/h.

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