Download Unit 6: Motion and Forces

Unit 6: Motion and Forces 2015 1
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Unit 6: Motion and Forces
VOCABULARY:
Term
Definition
Motion
Speed
Distance
How much ground an object has covered
during its motion; how far apart two points
are
Velocity
Frame of
reference
Acceleration
Vector
Force
Net Force
Inertia
Newton’s 1st
Law of Motion
(Law of Inertia)
objects at rest remain at rest, and objects in
motion remain in motion with the same
velocity, unless acted upon by an
unbalanced force
Newton’s 2nd
Law of Motion
the acceleration of an object increases with
increased force and decreases with
increased mass
Newton’s 3rd
Law of Motion
Equation (if applicable) or
example
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Gravitational
Force
Section 1:
Key Ideas:
 Analyze the motion of an object in terms of its position, velocity and acceleration as functions
of time
 Solve problems involving distance, velocity, speed and acceleration
 Create and interpret graphs
Vocabulary:





Motion
- Displacement
Speed
- Acceleration
Velocity
- Vector
Distance
Frame of Reference
Motion
 _______________________________________________________________________
_______________________________________________________________________
 relies on a frame of reference or something assumed to be stationary
 _______________________________________________________________________
o i.e. – you may be stationary as you sit in your seat, but you are moving 30 km/sec (≈19
mi/sec) relative to the Sun
Frame of Reference (Reference Point)
 _____________________________________________________________________________

none are truly stationary relative to all others – what is not moving in one is moving in another

Task:
o Using your body as the frame of reference, describe your classmate’s motion as s/he walks to
the classroom door. How does your frame of reference impact your description compared to
that of others? __________________________________
__________________________________________________________________
How does frame of reference explain why people thought the Earth was in the center of all
celestial bodies? _________________________________________
__________________________________________________________________
Speed
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
___________________________________________________________________________

a measure of how fast something moves, or the distance it moves, in a given amount of time
 Formula: s = d (distance)
t (time)


typically expressed in units of m/s
is considered _______________ when taking into account the total distance covered and the total
time of travel

is considered __________________when it does not change

is considered _______________________ when it represents a specific instant in time

What is the ball’s speed? ___________________________________________________
Practice problems – Speed:
1. If you walk for 1.5 hours and travel 7.5 km, what is your average speed?
2.
Calculate the speed of a bee that flies 22 meters in 2 seconds.
Draw the Speed-Distance-Time Triangle
Draw the distance time graph:
1. What is the speed from A – B? ________________________________________
2. What is the speed from B-C? __________________________________________
3. What is the speed from C-D? __________________________________________
4. What is the students average speed? _____________________________________
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Underneath each graph, describe what’s happening?
Thought question: Two birds perched directly next to each other, leave the same tree at the same time. They
both fly at 10 km/h for one hour, 15 km/h for 30 minutes, and 5 km/h for one hour. Why don’t they end up
at the same destination? ______________________________________
______________________________________________________________________________
Velocity

_______________________________________________________________________

_______________________________________________________________________

is considered ____________________when speed and direction do not change

changes as ________________________________________________ changes

is a vector

can be combined
o Example

If you are walking at a rate of 1.5 m/s up the aisle of an airplane that is traveling north
at a rate of 246 m/s, your velocity would actually be 247.5 m/s north

What is the formula for velocity? What is this similar to? _________________________
________________________________________________________________________
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Vector:

______________________________________________________________________________

drawn as an arrow which shows direction and magnitude (length of arrow)
o consists of two parts: tail and head (draw an example)
Combining Vectors:

can be combined/added

What is the total velocity for each of the people/animals on the conveyor belt?
_____________________
________________________ ___________________
Acceleration:

____________________________________________________________________________

is a vector

occurs when something is speeding up (+), slowing down (-), or changing direction

Formula: a = vf – vi (where vf is final velocity, and vi is initial velocity)
t(time)

typically expressed in units of m/s2

is always changing when traveling in a circle – centripetal
1. Is the ball accelerating? ________________________________________________
2. Describe the car’s acceleration: ______________________________________________
________________________________________________________________________
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3. What if I am traveling in my car at 60mph North constantly? What would my acceleration be?
__________________________________________________________
Practice Problems – Acceleration:
1. Tina starts riding her bike down a hill with a velocity of 2 m/s. After six seconds, her velocity is
14 m/s. What is Tina’s acceleration?
2. A motorcyclist goes from 35 m/s to 20 m/s in five seconds. What was his acceleration?
Momentum:

________________________________________________________________________________

is a vector

the product of an object’s mass and velocity

Formula: p=mv
(p is momentum, m=mass, v=velocity)

typically expressed in units of kg·m/s

_________________________________________________________________________________

makes an object harder to stop or change direction as it increases

can be transferred

is conserved
Practice Problems – Momentum:
1. What is the momentum of a 7.3 kg bowling ball moving at 8.9 m/s?
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2.
At a velocity of 8.5 m/s, Tim moves down a hill on an inner tube. If his mass is 59 kg, how much
momentum does he have?
Practice:

A helicopters speed increases from 25 m/s to 60m/s in 5 seconds. What is the acceleration of this
helicopter?

How far will you travel if you run for 10 minutes at 2.0m/s?

How much time would it take for the sound of thunder to travel 1,500 meters if sound travels at a
speed of 330m/s?

At a velocity of 10 m/s NE, Sadie moves down a mountain on her snowboard. If her momentum is
460 kg·m/s, what is her mass?
Section 2: Forces and Newton’s 3 Laws of Motion
 Key Ideas
 Interpret and Apply Newton’s 3 Laws of Motion
 Vocabulary






Inertia
1st Law
2nd Law
3rd Law
Friction
Tension
- Force
- Net force
- Applied force
- Normal force
- Air Resistance
- Spring
Force:

____________________________________________________________________________

typically measured in Newtons (kg•m/s2)
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
is a vector

can be combined to predict motion net force

Net force: ____________________________________________________________________
Types of Forces:

Contact Forces
o Applied
o Normal
o Friction
o Air Resistance
o Tension
o Spring
Applied Force:


Non-Contact Forces
o Gravity
o Electromagnetic
any push or pull on an object created from another source (person, animal, another object, etc.)
Normal Force:

the support force exerted on an object directly related to weight (gravity)

consequence of Newton’s 3rd Law

_____________________________________________________________________________

Draw and label the pictures
Friction:

exerted by a surface as an object moves across it or attempts to move across it

___________________________________________________________________________

depends on the type of surfaces and the normal force (weight)
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Air Resistance:

____________________________________________________________________________

acts upon objects as they travel through the air

___________________________________________________________________________

most noticeable for objects traveling at fast speeds
Tension:

force that is transmitted through a string, rope, cable or wire when it is _______________ tight by
forces acting from opposite ends

directed along the length of the wire and ______________ equally on the objects on the opposite
ends of the wire
Spring:

________________________________________________________________________________

for most springs, the magnitude of the force is directly proportional to the amount of stretch or
compression of the spring
Gravity:

_____________________________________________________________________________

factors:
 distance – increased distance  less gravitational pull or vice versa
 mass – increased mass  more gravitational pull or vice versa

Why does the force of gravity have more of an impact on holding our solar system together
compared to holding the parts of an atom together? _________________
___________________________________________________________________
Electromagnetic Force:
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
force that moving charges exert on one another

results from the repulsion of like charges and the attraction of opposites
Vector Review:

a quantity that has both direction and magnitude (size)

drawn as an arrow which shows direction and magnitude (length of arrow)
o consists of two parts: tail and head

Draw the vectors. Then describe the direction and relative magnitude of each ball based on the
vector.
Combining Vectors Review:

can be combined/added to help determine net force
o the overall force acting on an object when all of the forces acting on it are combined
o Draw the picture and determine the net force.
Free Body Diagrams:

visuals that help show net force
o use a square and draw all forces acting on the object.
o remember size and direction of vector arrows are important!
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o Draw the diagram and determine the net force.
Determine the net force:
Fnorm = 10 N
Ffric = 5 N
Fapp = 15 N
Fgrav = 10 N
Net force: __________________________
Net force:_____________________
Newton’s Laws of Motion:
Newton’s 1st Law of Law of Inertia:

objects at rest remain at rest, and objects in motion remain in motion with the same velocity, unless
acted upon by an unbalanced force

also considered the Law of Inertia

How is this illustrated when riding in a car? Can you think of other experiences where this is
illustrated? _________________________________________________________
________________________________________________________________________
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Inertia:

the resistance of an object to a change in the speed or the direction of its motion

________________________________________________________________________

Which has more inertia: a car or a person? Why? ____________________________
________________________________________________________________________
Newton’s 2nd Law of Motion:

the acceleration of an object increases with increased force and decreases with increased mass

_________________________________________________________________________________

Formula: F = ma (or a = F/m)
Practice Problems – 2nd Law:
1. What net force is needed to accelerate a 24 kg dogsled to a rate of 3 m/s2?
2.
A 1.5 kg object accelerates across a smooth table at a rate of 0.5 m/s2? What is the unbalanced
force applied to it?
Newton’s 3rd Law of Motion:

states that every time one object exerts a force on another object, the second object exerts a force
that is equal in size and opposite in direction back on the first object

Can you think of any experiences/examples where this is illustrated? ________________
________________________________________________________________________
Section 3: Gravitational Force

Key Ideas
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o Explore how the gravitational force between two objects depends on their masses and the
distance between them.

Vocabulary
o Gravity
o Gravitational Constant
Law of Universal Gravitation:
Where:
Fg = Force of Gravity
G = the gravitational constant (6.67 x 10-11 N *m2/kg2)
M1= Mass of object 1
M2 = Mass of object 2
d = distance between two objects
Gravity ____________________________________________________________________!!!!!!
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SECTION 3:
Key Ideas:
•
•
What are Synthesis (creating)
Decomposition (separating)
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•
Combustion (burning)
•
Displacement/Replacement (switching)
SYNTHESIS (CREATING)
•
________________________________________________________________________
•
Ex: Synthesis of Carbon Dioxide
2CO(g) + O2(g) → 2CO2(g)
DECOMPOSITION (SEPARATING)
•
_______________________________________________________________________
•
Ex: Electrolysis of water to make hydrogen and oxygen
•
2 H2O ---> 2 H2 + O2
COMBUSTION (BURNING)
•
______________________________________________________________________
•
Oxygen reacts with another element or compound to form water (H2O), carbon dioxide (CO2) and
heat
•
_______________________________________________________________________
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DISPLACEMENT/REPLACEMENT (SWITCHING)
•
Two types: Single replacement and double replacement
•
Single replacement (substitution):
___________________________________________________________________________
_________________________________________________________
•
•
Ex: Zn + 2 HCl → ZnCl2 + H2
•
Ex:
Double Replacement: _______________________________________________
__________________________________________________________________
•
Ex: AgNO3 + HCl → AgCl + HNO3
•
Ex: Fe2O3 + HCl → FeCl3 + H2O
CHEMICAL VS NUCLEAR RXN:
Chemical Reaction
•
Atoms are rearranged, and chemical
bonds are broken and reformed
•
New substance is formed
Nuclear Reaction
•
__________________________________
•
Involves at least two nuclei, where one
has to have all its electrons removed, by
bringing it to very high temperatures. Why
must the electrons be removed?
•
A neutron is then “slammed” into another
nucleus, causing the nucleus to break
apart (fission) or combine to create a new
nucleus (fusion)
C6H12O6 + 6O2  6CO2 + 6H2O + energy
(respiration)