Transcript Chapter 3

Chapter 11
Motion
Key Concepts
What is needed to describe
motion completely?
How are distance and
displacement different?
How do you add displacement?
Frame of Reference
To describe motion accurately and
completely, a frame of reference is
necessary.
A system of objects that are not
moving with respect to each other.
Frame of Reference
Relative Motion
Relative motion is movement
in relation to the frame of
reference.
Distance
Distance is the length of a
path between two points.
5m
Total Distance is 20m
10m
10m
Displacement
Distance between two points.
Displacement has a magnitude
(distance).
Displacement also has a direction
(north).
Displacement is a vector quantity.
Straight Line Displacement
Displacement is 1.75km
To the right
1km
.75km
Straight Line Displacement
Displacement is 0.25km
To the right
.75km
1km
Straight Line Displacement
Displacement is 0.25km
To the left!!!!
1.25km
1km
Distance is 20m
10m
10m
Displacement is 14m
at an angle of 45°
Homework 11-1
Worksheet 11-1
11-1 Assessment: 1-8
Book - Page: 331
Due: 2/2/09
11-2 Key Concepts
How are instantaneous speed and
average speed different?
How can you find the speed from a
distance-time graph?
How are speed and velocity
different?
How do velocities add?
Motion and Speed
Position: A point of reference.
Motion: A change of position.
Speed(v)
Rate at which an object changes
position.
Speed =(meters/second)
v = (m/s)
The rate of motion at a
given instant.
Instantaneous Speed
Constant Speed
A speed that does not vary.
Average Speed
Total distance traveled divided
by the total time of travel.
Total distance
Average Speed = total time
d
v=
t
Average Speed
Oneonta
Norwell
Calculating Speed
Distance {d, meter(m)}
Time {t,seconds(s)}
Speed {v, meters per
second(m/s)}
v = d/t
Speed Equation
d
v
t
Wheel of Answers
Find Speed(v)
d
v t
d
v=
t
Find Distance(d)
d
v
t
d = vxt
Find time(t)
d
v
t
d
t= v
Steps to
Solving Problems
1. Read the problem carefully!!!
2. Pick out the information needed to
solve the problem. Given
3. What is it that you have to find:
Find
4. What equations are needed to solve
the problem: Equation
Solve
Box your answer – units are
important!!!!
5. Solve the problem:
6.
Example
Mr. Clune is traveling to Chatham
this weekend. Chatham is
approximately 70 miles away. A
good estimate of his speed is
50 miles per hour.
How long will it take to get there?
Given: d = 70 mi
v = 50 mi/hr
Find: t = ?
?
Let’s go to the
Wheel of Answers!!!!
Equation:
Find time(t)
d
v
t
d
t= v
Given: d = 70 mi
v = 50 mi/hr
Find: t = ?
d
Equation: t =
v
70 mi
Solve: t = 50 mi/hr
t = 1.4 hr
Let’s Practice
Page 333
Problems: 1-2
Page 337
Problems: 8-9
Page 351
Problems: 19-20
Due: 2/4/09
Example
d = 400 km
t = 5 hr
Given: d = 400 km
t = 5 hr
Find: Average Speed (v) = ?
Equation: v = d/t
Solve: v = d/t
v = (400 km) / (5 hr)
v = 80 km/hr
Velocity
Velocity: The speed and direction of
an object. (Vector quantity.)
50 km/hr
50 km/hr
Graphing Speed
Distance(m)
50
D
40
30
B
20
10
C
A
10
20
30
40
50
Speed
A: Forward
B: Zero
C: Backward
D: Forward
Faster than A
Time(s)
Slope of d vs. t is Speed
50
Distance(m)
D
40
30
B
C
20
10
A
10
20
30
Time(s)
40
50
Slope of the d vs. t curve
Speed!!
rise y
Slope = run = x
distance
y
=
x
time
= Speed
50
Distance(m)
D
40
30
B
C
20
10
A
10
20
30
Time(s)
40
50
Line A
Distance(m)
50
D
40
30
B
20
10
C
A
10
20
30
Time(s)
40
50
Graphing Speed
Line A:
Line B:
Line C:
Line D:
d
v
=
= 2m/s
t
20m
10s
0m
= 0m/s
10s
10m
= -1m/s
10s
40m
= 4m/s
10s
Graphing Speed
D
4
3
2
A
Speed(m/s)
1
B
0
10
-1
-2
Time(s)
20
30
C
40
50
Combining Velocities
Velocity, like displacement, is
a vector quantity.
Velocity vectors can be
added together to find a
resultant.
500mi/hr
550mi/hr
50mi/hr
450mi/hr
50mi/hr
50mi/hr
Homework 11-2
Worksheet 11-2
Due: 2/5/08
Allan
Becky
20
Cindy
Distance (m)
15
10
5
0
-5
-10
5
10
15
20
Time (s)
Acceleration
Acceleration (a, m/s²): The rate of
change of velocity.
Change in Speed!!
Accelerate – Faster
Decelerate – Slower
Change in Direction
Turning!!
Constant Acceleration
A steady change in velocity.
Free Fall
Free Fall
The movement of
an object toward
Earth because of
gravity.
9.8m/s2
32ft/s2
t=0s d=0m v=0m/s a=9.8m/s2
t=1s d=4.9m v=9.8m/s a=9.8m/s2
t=2s d=19.6m v=19.6m/s a=9.8m/s2
Free Fall
Acceleration
Acceleration (a) = change in velocity
time (t)
v
a =
t
Delta
“Change in”
Acceleration
a = v = vf - vi
t
t
a
v
vf
vi
t
– acceleration
– change in velocity
– final velocity
– initial velocity
- time
Acceleration Equation
vf - vi
a t
Acceleration
vf - v i
a t
vf - vi
a= t
Time
vf - v i
a t
vf - vi
t= a
Change in Velocity
vf - v i
a t
vf – vi= at
Example: A car’s velocity changes from
0 m/s to 30 m/s in 10 s. Calculate the car’s
average acceleration.
Given: vi = 0 m/s
Find: a = ?
vf = 30 m/s
t = 10 s
Equation : a = vf - vi
t
Solve : a = (30 m/s) - (0 m/s)
10 s
a = 3 m/s²
Graphing Acceleration
Velocity (m/s)
D
5
4
3
2
1
A
1
B
2
C
3
4
5
Time(s)
Slope of a Velocity-Time Graph
is Acceleration
Accleration vs. Time
2
Accelration(m/s )
12
10
8
9.8m.s2
6
4
2
0
1
2
3
4
Time(s)
5
6
Velocity vs. Time
Velocity(m/s)
60
50
Linear Curve
40
30
20
10
0
1
2
3
4
Time(s)
5
6
Distance(m)
Distanced vs. Time
140
120
100
80
60
40
20
0
Non-Linear Curve
1
2
3
4
Time(s)
5
6
Homework
Worksheet 11-3
Math Practice: 1-4
Page: 346
Due: 2/12/09
Test: 2/13/09
A car traveling at 10 m/s starts to decelerate
steadily. It comes to a complete stop in
20 seconds. What is its acceleration?
An airplane travels down a runway for
4.0 seconds with an acceleration of 9.0 m/s2.
What is its change in velocity during this time?
A child drops a ball from a bridge. The ball strikes the
water under the bridge 2.0 seconds later. What is the
velocity of the ball when it strikes the water?
A boy throws a rock straight up into the air. It reaches the
highest point of its flight after 2.5 seconds. How fast was
the rock going when it left the boy's hand?
A car traveling at 10 m/s starts to decelerate
steadily. It comes to a complete stop in
20 seconds. What is its acceleration?
Homework
Worksheet
Word Wise - Math
Due: 2/13/09
Test: 2/13/09
Connecting Motion and Forces
Force (newton, N): A push or pull one
body exerts on another.
Earth
Balanced Forces
Balanced Forces: Forces on an object that
are equal in size and opposite in direction.
Unbalanced Forces
Unbalanced Forces: Forces on an
object are not equal resulting in a Net
Force.
5N
3N
Net Force
A Net Force on an object always
changes the velocity of the object.
2N
Inertia
Inertia (mass): The tendency of an
object to resist any change in its
motion.
1kg
25 kg
The more mass an object
has, the greater its inertia.
Newton’s First Law
The Law of Inertia
An object moving at a constant
velocity keeps moving at that
velocity unless a net force acts on it.
An object at rest, will remain at rest
unless a net force acts on it.
Friction
Friction: The force opposes motion
two surfaces that are touching each
other.
Gravity
Gravity: Every object in the universe
exerts a force on every other object.
This force is Gravity!!!
Weight
Weight: The measure of the force
of gravity on an object.
Weight
Moon
(16.7 lb)
Earth
(100 lb)
Jupiter
(254 lb)
Physical Science
Section Wrap-up Pg: 86
Vocab: 1-10*Pg: 89
Chk Conc: 1-10* Pg:90
Due:10/5/05
* Write out questions!!!