Download Chapter 5: Matter in Motion

Chapter 5:
Matter in Motion
Material on Final Exam
Section 1: Measuring
Motion
• Objectives:
• Describe the motion of an object by the position of the
object in relation to a reference point
• Identify the two factors that determine speed
• Explain the difference between speed and velocity
• Analyze the relationship between velocity and
acceleration
• Explain how changes in motion can be measured and
represented in a graph
Section 1: Measuring Motion
• Everything moves
• Even if it does not look like it
• When we see things move, it is based on a
__________________________
reference point
Motion is when an object changes position over
• _____________
time relative to a reference point
1/26 Agenda
Continue Notes:
• How to solve Velocity math problems
• Practice calculating speed, time, and
distance
• Begin some HW problems for practice
HW:
Pg 1: items I, II, III
Pg 2, and Pg 3
Section 1: Measuring Motion
• What is speed?
Speed is the distance traveled by an object divided
• _________
by the time taken to travel the distance
• SI unit is _________
m/s
• Other units: mi/h, km/h, ft/s
Section 1: Measuring Motion
• Average Speed
WHOLE
• For the __________
time
= total distance
total time
• General speed
• For a _________
short
time
= distance
time
Section 1: Measuring
Motion
1. Write the formula
2. Identify knowns
and unknowns
3. Plug in numbers
4. “Chug”: Solve
and circle
What is the average
speed for the whole
trip?
Section 1: Measuring
Motion
1. Write the formula
2. Identify knowns
and unknowns
3. Plug in numbers
4. “Chug”: Solve
and circle
A snail moves 1m in
100 seconds. What is
the speed ?
Section 1: Measuring
Motion
1. Write the formula
2. Identify knowns
and unknowns
3. Plug in numbers
4. “Chug”: Solve
and circle
A car is driving along
at 25km/hr. How
long will it take me
to drive 400km?
Section 1: Measuring
Motion
1. Write the formula
2. Identify variables
3. Plug in numbers
4. Solve and circle
A bee is flying by at
a speed of .75 m/s.
How far will the bee
travel in 60 seconds?
Section 1: Measuring Motion
Speed ≠ Velocity
Velocity is the speed of an object in a given direction
• _____________
direction
• Velocity MUST include a ___________!
Section 1: Measuring Motion
• Which is it? Speed or Velocity?
• 7 miles per hour
• 2.345 inches/minute east
• 18.7 ft/s down
• 7.77 km/day
Section 1: Measuring Motion
• Changes in Velocity
speed
• Could be a change in the actual ________
direction
• Could be a change in ______________
both
• Could be _________!
Section 1: Measuring Motion
• Combining Velocities
• When you combine velocities together, you have to
look at the direction
ADD
• If they are in the same direction, you ______ them
SUBTRACT THEM
• If they are in different directions, you ______________
• ***MAKE SURE TO INCLUDE THE DIRECTION***
Section 1: Measuring Motion
• Combining velocities
• I walk 3 ft/s down while the escalator pushes me 5 ft/s
up. What is the resultant velocity?
• A bird is flying at a velocity of 5km/hr west when a gust
of wind pushes her with a velocity of 10 km/hr west.
What is the resultant velocity?
Section 1: Measuring Motion
Distance-Time graphs
• This type of graph is based on the most basic
things we need to know about the motion of an
distance
time
object (______________
and _________).
X axis
• Time goes on the ___
• Position / Distance goes on the ___-axis
Y
away from start, we
• IF the object moves _________
increase
__________________
distance (+)
• IF the object moves ____________
start, we
toward
decrease distance (-)
____________
• Draw each section a bit at a time
• No best fit lines!
Section 1: Measuring Motion
Dance Class Movement
100
90
Distance from wall (feet)
80
70
60
50
40
30
20
10
0
0
15
30
45
60
75
Time (seconds)
90
105
120
135
150
Section 1: Measuring Motion
• What is happening from 0-30 seconds?
• What is happening from 0-60 seconds?
• From 60-75 seconds?
• From 75-90 seconds?
• From 90-105 seconds?
• 105 to 120?
• 120 to 135?
• 135 to 150?
Section 1: Measuring Motion
• What is the speed of the dancer from…
• 30 to 60 seconds?
• 90 to 105 seconds?
• 135 to 150 seconds?
Section 1: Measuring Motion
• Acceleration
not always mean “speed up”!
• Does ________
Acceleration is the rate at which velocity
• ___________________
changes
• An object accelerates if its speed, direction, or both
change
Section 1: Measuring Motion
• Increase in velocity
• ________________________
Positive acceleration
• Do not say “speeding up”
• Decrease in velocity
acceleration
• Negative
__________________________
• Do not say “slowing down”
Section 1: Measuring Motion
• Calculating Average Acceleration
m/s2
• Units for acceleration:__________
• How? m
=mx1
=m
s
s x s
s2
s
Section 1: Measuring Motion
• Math Practice
• Use the equation for average acceleration to do the
following problem.
• A plane passes over point A at a velocity of 240 m/s
north. Forty seconds later, it passes over point B at a
velocity of 260 m/s north. What is the plane’s average
acceleration?
•
•
•
•
Write the formula
Show your work
Solve with correct number
Include correct units
Section 1: Measuring Motion
• Math Practice—Solving for Acceleration (a)
• A roller coasters velocity at the top of the hill is 10
m/s. Two seconds later it reaches the bottom of the
hill with a velocity of 26m/s. What is the acceleration
of the coaster?
Section 1: Measuring Motion
• Math Practice—Solving for time (t)
• How long will it take a car to go from 0 to 45 km/hr if
they are accelerating at 5 km/hr2?
Section 1: Measuring Motion
• Math Practice—Solving for starting/initial velocity (vi)
• You roll a bowling ball for 4 s. The ball traveled at a
constant acceleration of 2 m/s2 down the lane and
was traveling at a speed of 9 m/s by the time it
reached the pins at the end of the lane. How fast
was the ball going when it left Tim’s hand?
Section 1: Measuring Motion
• Math Practice—Solving for final velocity (vf)
• If a truck, with an initial velocity of 10 m/s,
accelerates at a rate of 30 m/s2 for 3 seconds, what
will its final velocity be?
Section 1: Measuring Motion
Section 1: Measuring Motion
• Recognizing Acceleration on a Graph
• Velocity has to CHANGE over time
Section 1: Measuring Motion
• Circular Motion:
Continuous Acceleration
• You are always changing
direction in a circle!
Centripetal
• _________________
acceleration
_____________________
is
the acceleration that
occurs during circular
motion
• Not “speeding up”
(Positive acceleration)
• Not “slowing down”
(Negative acceleration)
direction
• But changing
____________________!
Section 1: Measuring
Motion
• Please answer the following questions on your
objective sheet
• Describe the motion of an object by the position of the
object in relation to a reference point
• Identify the two factors that determine speed
• Explain the difference between speed and velocity
• Analyze the relationship between velocity and
acceleration
• Explain how changes in motion can be measured and
represented in a graph
Section 2: What is a Force?
• Objectives
• Describe forces, and explain how forces act on
objects.
• How do you determine the net force when more than
one force is acting on an object?
• Compare balanced and unbalanced forces.
• Describe how unbalanced forces cause changes in
motion.
Section 2: What is a Force?
• What is a force?
push or
• A force is a _______
pull
_________
exerted on an
object in order to
change the direction of
the object
• Often causes a
change in motion
• Unit of force is the
Newton (N)
_______________
Section 2: What is a Force?
• Forces
• Any time you push or pull an object, you are exerting a
force.
a force does not guarantee movement
• However, a _________________________________________!
Section 2: What is a Force?
• Unseen Forces and Receivers of
Force
• Sometimes we ______________
cannot see the forces
that are in place
• Gravity
• Magnetism
• Static electricity
Section 2: What is a Force?
Determining Net Force
The net force is the combination of
all of the forces
_______________________
acting on an object
• SAME direction? _______!
Add
Subtract
• OPPOSITE direction? ____________
Section 2: What is a Force?
• Balanced and Unbalanced Forces
net forces
• Look at the ________________
to see if forces are
balanced or not
• If the net force is
zero…
• The forces are
balanced
_________________!
• No change in
motion
• If the net force is not
zero…
• The forces are
________________!
unbalanced
• There is a change
in motion
Section 2: What is a Force?
• Please answer the following on your objective sheet
• Describe forces, and explain how forces act on
objects.
• How do you determine the net force when more than
one force is acting on an object?
• Compare balanced and unbalanced forces.
• Describe how unbalanced forces cause changes in
motion.
Section 3: A Force that
Opposes Motion
• Please answer the following on your objective sheet
• Describe friction
• Explain why friction occurs
• List the two types of friction, and give examples of
each
Section 3: A Force that
Opposes Motion
• Why does it stop?
• Unbalanced force!
Friction
• ____________
is a force that opposes motion between
two surfaces that are in contact
rough surface
• Everything has a ________
Section 3: A Force that
Opposes Motion
• The microscopic view of surfaces shows little hills
and valleys
• When they come in contact with each other, they
stick together and slow down the movement
Section 3: A Force that
Opposes Motion
• What is the difference?
weight
• The ______________________________!
weight
• More _____________
= more _____________
friction
Section 3: A Force that
Opposes Motion
• Rough surfaces and friction
rougher
• The ________________
the surface, the more hills and
valleys the two items can get “stuck” on
Section 3: A Force that
Opposes Motion
Types of Friction
• Kinetic Friction
• Friction between
moving
_____________
surfaces
• _____________
Sliding
Rolling
• _____________
• Static Friction
• Friction between
nonmoving
________________
objects
• _____
No movement
because forces are
balanced
Section 3: A Force that
Opposes Motion
Section 3: A Force that
Opposes Motion
• Friction: Harmful and Helpful
• No friction?
• Could not push tires against ground to move car
• Could not use brakes to stop car
• With friction?
• Car parts rub against each other and wear out
• Part of everyday life!
• Writing, holes in socks, slipping on ice, climbing a hill
Section 3: A Force that
Opposes Motion
• Please answer the following on your objective sheet
• Describe friction
• Explain why friction occurs
• List the two types of friction, and give examples of
each
Section 4: Gravity—A
force of Attraction
• Objectives
• Describe gravity and its effect on matter
• Describe the difference between mass and weight
Section 4: Gravity—A
force of Attraction
• What is gravity?
• Gravity is a force of
attraction
_______________
between
objects that is due to their
masses
• Gravity can affect an
object by…
speed
• Changing its ________
• Changing its
direction
__________________
• Changing its speed _______
AND
direction
Section 4: Gravity—A
force of Attraction
• The Effects of Gravity on Matter
mass
• All objects have ________
• All objects experience an ______________
attraction towards one
another due to gravity
• Why don’t we get sucked into other people, items, or
objects?
_______________
We do not have
enough mass!
_______________
Section 4: Gravity—A
force of Attraction
• Newton and the study of
gravity
• Newton was able to
recognize that items falling
and the moon in orbit are
caused by _________________
gravity
• Newton’s Law of Universal
Gravitation describes the
relationship between
force
gravitational _________,
distance
mass and ____________
_______,
• Applies to everything in the
universe!
Section 4: Gravity—A
force of Attraction
Law of Universal Gravitation
Gravitation force
Gravitation force
• Part 1: _______________________
• Part 2: ________________________
______________________________
______________________________
increases as mass increases
decreases as distance
__________________________
increases
Section 4: Gravity—A
force of Attraction
• Weight as a measure of Gravitational Force
not the same
• Weight and mass are ______________________
• Mass—the amount of _________
mass in an object (kg)
• Weight—measure of ________________________________
on
gravitational force
an object (N)
Section 4: Gravity—A
force of Attraction
• Weight can be calculated using the formula
𝑊𝑒𝑖𝑔ℎ𝑡 = 𝑚𝑎𝑠𝑠 𝑥 𝑔𝑟𝑎𝑣𝑖𝑡𝑦
𝑊 = 𝑚𝑔
• Units
Newtons (N)
• Weight: ______________
Kilograms (kg)
• Mass: _______________
convert
• If in grams, must _______________
m/s2
• Gravity: _______
9.8 m/s2
• On Earth, the value is _________________
Section 4: Gravity—A
force of Attraction
• Math Practice: Solving for Weight (w)
• A cat has a mass of 7 kg. What would the weight of
the cat be on Earth?
Section 4: Gravity—A
force of Attraction
• Math Practice: Solving for mass (kg)
• On a trip to Mars, you meet an alien. When you
bring it back to Earth, you find that it weighs 245 N
on Earth. What is the mass of the alien?
Section 4: Gravity—A
force of Attraction
• Math Practice: Solving for gravity (g)
• The same alien from before (mass of 25 kg) says he
only weighs 90N on his home planet. What is the
gravity on Mars?
Section 4: Gravity—A
force of Attraction
• Please answer the following on your objective sheet
• Describe gravity and its effect on matter
• Describe the difference between mass and weight