Download Newton`s Laws Notes Packet - Answer Key PDF

Vocabulary
Term
Definition
Force
A push or pull.
Inertia
The resistance of a body to changes to its state of
motion.
Newton
The metric unit of force.
Net Force
The sum of all forces acting on an object.
Newton’s 1st Law
An object at rest will remain at rest unless acted on by an
unbalanced force; an object in motion continues with
constant speed and direction in a straight line unless
acted on by an unbalanced force.
Newton’s 2nd Law
Force = mass x acceleration
Newton’s 3rd Law
For every action, there is an equal and opposite reaction.
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Newton’s 1st Law of Motion
Newton’s 1st Law of motion
Main Ideas
is also know as the
law of
An object at rest
will remain at rest
Inertia
an object in motion
continues with
constant speed and
direction in a straight
line
Definition of
inertia:
The resistance of a body to
changes to its state of
motion.
Unless acted upon
by an
Force
A push or pull.
Applying Newton’s 1st Law of
motion
Explain according to Newton’s 1st law of motion what would happen to the person in the car
below if theyFIRST
crashed
intoOF
theMOTION
wall using (aka:
the terms
inertia, state of motion, and unbalanced
NEWTON’S
LAW
_______________________________)
force.
States:
The
person
and the car both have inertia, thus will continue in motion unless an unbalanced force
An
Object
____________________________________________________________
acts
on
them.
When the car crashes into the wall and unbalanced force acts upon the car to change
____________________________________________________________________
its
state
of
motion,
the car stops; however, there is no unbalanced force acting on the person so they
____________________________________________________________________
continue moving forward.
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Inertia is the property of an object that resists changes in motion.
Class Work
1. Which has more inertia a bowling ball or a golf ball? Bowling Ball
2. Objects with more mass have more inertia and are more resistant to changes in their
motion.
3. Mac and Tosh are arguing in the cafeteria. Mac says that if he flings the Jell-O with a
greater speed it will have a greater inertia. Tosh argues that inertia does not depend upon
speed, but rather upon mass. Who do you agree with? Explain why.
Tosh because inertia depends on mass and mass alone.
4. Fred spends most Sunday afternoons at rest on the sofa, watching pro football games and
consuming large quantities of food. What effect (if any) does this practice have upon his
inertia? Explain.
Increases inertia.
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Notes – Newton’s Second Law
John and Joe have a grocery cart race. John pushes a loaded grocery cart; Joe pushes an empty
grocery cart. Joe wins the race. Why? Joes has less mass to push, thus can accelerate his cart
faster.
John
Joe
Joe and his little brother Junior have a grocery cart race. Joe wins the race. Why? Joe can push
with a greater force than junior can.
Joe
Junior
1. When a grocery cart is pushed by a person, a(n) unbalanced force acts on
the cart and the cart accelerates.
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2. The acceleration of an object is directly proportional to the net force acting on it. This means
that, as the net force acting on the object increases, the acceleration of the object increases.
Newton’s 2nd Law of Motion states:
The acceleration of an object is directly proportional to the net force acting on the object and
inversely proportional to the object’s mass.
2nd law
abbreviated using
symbols:
∑F = ma
∑F = sum of the forces
m = mass
a = acceleration
Newton’s 2nd law relates the net force on an object, the mass of the object, and acceleration.
• It states that the stronger the net force on an object, the faster the object will accelerate.
• If twice the net force is applied, the acceleration will be twice as great.
• The acceleration of an object is directly proportional to the net applied force and
inversely proportional to the mass. (in other words if the force increases, the acceleration
increases and if the mass increases the acceleration decreases.)
∑F
a
m
NEWTON’S 2ND LAW
Formula
Want to find
What you know
A = F/m
acceleration (a)
force (F) and mass (m)
F = ma
force (F)
acceleration (a) and mass (m)
m = F/A
mass (m)
acceleration (a) and force (F)
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Formula
nd
Newton’s 2 Law
F = ma
No Acceleration
Net Force
Add forces
Same Direction
Subtract
forces
Net force is
Zero.
Objects are at rest or
moving with
constant speed.
Opposite Direction
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NEWTON’S SECOND LAW
Formula
Want to find
What you know
acceleration=Force/mass
force (F) and mass (m)
Force =mass x acceleration
acceleration
(a)
force (F)
Mass = Force/ acceleration
mass (m)
acceleration (a) and force (F)
acceleration (a) and mass (m)
F
a
m
Class Work
1. A 1650 kg car accelerates at a rate of 4.0 m/s2. How much force is the car's engine
producing?
Looking For
Force
Given
m=1650 kg
a=4 m/s2
Relationship
F=ma
Solution
=(1650 kg) x (4m/s2)
=6600 N
2. A tennis ball, 0.314 kg, is accelerated at a rate of 164 m/s2 when hit by a professional
tennis player. What force does the player's tennis racket exert on the ball?
Looking For
Force
Given
m=0.314 kg
a=164 m/s2
Relationship
F=ma
Solution
=(0.314 kg) x (164m/s2)
=51.5 N
3. A crate is dragged across an ice covered lake. The box accelerates at 0.08 m/s2 and is
pulled by a 47 N force. What is the mass of the box?
Looking For
Mass
Given
F=47 N
a=0.08 m/s2
Relationship
m=F/a
Solution
= 47 N / 0.08 m/s2
=587.5 kg
Group Work
1. What is the rate of acceleration of a 2,000-kilogram truck if a force of 4,200 N is used to
make it start moving forward?
Looking For
Given
Relationship
Solution
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Acceleration
F=4200 N
m=2000 kg
a=F/m
2.1 m/s2
2. What is the acceleration of a 0.30 kilogram ball that is hit with a force of 25 N?
Looking For
Acceleration
Given
F=25 N
m=0.30 kg
Relationship
a=F/m
Solution
83.33 m/s2
3. How much force is needed to accelerate a 68 kilogram-skier at a rate of 1.2 m/sec2?
Looking For
Force
Given
m=68 kg
a=1.2 m/s2
Relationship
Solution
81.6 N
F=ma
4. What is the mass of an object that requires a force of 30 N to accelerate at a rate of 5
m/sec2?
Looking For
Mass
Given
F=30 N
a=5 m/s2
Relationship
Solution
6 kg
m=F/a
5. What is the force on a 1,000 kilogram-elevator that is falling freely under the acceleration
of gravity only?
Looking For
Force
Given
m=1000 kg
a=9.8 m/s2
Relationship
Solution
9800 N
F=ma
6. What is the mass of an object that needs a force of 4,500 N to accelerate it at a rate of 5
m/sec2?
Looking For
Mass
Given
F=4500 N
a=5 m/s2
Relationship
Solution
900 kg
m=F/a
7. What is the acceleration of a 6.4 kilogram bowling ball if a force of 12 N is applied to it
and it experiences a 4-N frictional force?
Looking For
Acceleration
Given
m=6.4 kg
F=12 N
Relationship
a=F/a
Solution
1.25 m/s2
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HomeWork (10 points)
1. What is the rate of acceleration of a 1,000-kilogram truck if a force of 4,200 N is used to
make it start moving forward?
Looking For
Acceleration
Given
m=1000 kg
F=4200 N
Relationship
a=F/m
Solution
4.2 m/s2
2. What is the acceleration of a 0.30 kilogram ball that is hit with a force of 50 N?
Looking For
Acceleration
Given
m=0.30 kg
F=50 N
Relationship
a=F/m
Solution
166.67 m/s2
3. How much force is needed to accelerate a 68 kilogram-skier at a rate of 1.2 m/sec2?
Looking For
Force
Given
m=68 kg
a=1.2 m/s2
Relationship
Solution
81.6 N
F=ma
4. What is the mass of an object that requires a force of 30 N to accelerate at a rate of 5
m/sec2?
Looking For
Mass
Given
F=30 N
a=5 m/s2
Relationship
m=F/a
Solution
6g k
5. What is the mass of an object that needs a force of 4,500 N to accelerate it at a rate of 5
m/sec2?
Looking For
Mass
Given
F=4500 N
a=5 m/s2
Relationship
m=F/a
Solution
900 kg
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Newton’s 3rd Law
ACTION
REACTION
states that
Wall hits fist
For every action there is
an equal and opposite
reaction.
Forces are equal in
Bug hits
windshield
Forces are opposite in
Ball hits bat.
magnitude
direction
Bar pushes
downward.
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