Unit 6: Motion and Forces 2015 Stevens

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Unit 6: Motion and Forces VOCABULARY:

Term Definition Equation (if applicable) or

example

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

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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 - Force

1st Law - Net force

2nd

Law - Applied force

3rd

Law - Normal force

Friction - Air Resistance

Tension - 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:

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)

Non-Contact Forces

o Gravity

o Electromagnetic

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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:

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? _________________________________________________________

________________________________________________________________________

Fgrav

= 10 N

Ffric

= 5 N

Fnorm

= 10 N

Fapp

= 15 N

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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/kg

2)

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

C6H12O6 + 6O2 6CO2 + 6H2O + energy

(respiration)

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)