Download Unit 7 lesson 1 Newton`s Laws

VI. NEWTON’S LAWS OF MOTION
A. NEWTON’S 1ST LAW
HTTPS://VIMEO.COM/28965409 NEWTONS LAWS
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1. An object at rest remains at rest,
and an object in motion
remains in motion at constant
speed and in a straight line
unless acted on by an
unbalanced force
2. Part 1: Objects at Rest
•
An object that is not moving will continue to not
move until a force is acted upon it
3. Part 2: Objects in Motion
•
An object will continue to move with the same
velocity until a force acts upon it
4. Friction & Newton’s 1st Law
•
The unseen force that will slow down & stop an object in motion
•
Inertia= the tendency of all objects to resist any change in
motion
That is why the object at rest will stay at rest & in motion “wants”
to stay in motion
5. Newton’s 1st law= Law of Inertia
•
6. Mass is a measure of inertia
•
•
Small mass= less inertia
Changing motion of a small mass is easier than changing the
motion of a large mass
B. NEWTON’S 2ND LAW OF MOTION
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1. The acceleration of an
object depends on the
mass of the object and
the amount of force
applied
2. Part 1: Acceleration
depends on Mass
•
The more mass the more
force it takes to get the
object into motion
3. Part 2: acceleration
depends on Force
•
The greater the force
applied to the object the
greater the acceleration
4. Newton’s 2nd law expressed mathematically:
https://youtu.be/O4CDqKahFSk
a=
or
F
F= m x a
m
• What is the acceleration of a 3 kg mass if a force
.
of 14.4N is used to move the mass? (1N = 1kg ms2)
a= F
m
.
a= 14.4 kg m/s2 = 4.8m/s2
3kg
C. NEWTON’S 3RD LAW OF MOTION
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1. Whenever one object exerts a force on a 2nd
object, the 2nd object exerts an equal and
opposite force on the 1st
2. All forces act in pairs
•
Ex: space shuttle thrusters push exhaust gasses
downward as the gasses push the shuttle upward
with an equal force moving the shuttle upward
III. MOMENTUM
A. MOMENTUM MASS AND VELOCITY
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1. Momentum (p)= the product of the mass and
velocity of an object
2. More momentum the harder it is to stop or change
the direction
3. Can be calculated as:
P= m x v
4. with the units kgm/s in a direction
B. LAW OF CONSERVATION OF
MOMENTUM
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1. When an object hits
another object some or all
of its momentum of the first
object is transferred to the
object that it hit
2. The law of conservation of
momentum states that
any time objects collide,
the total amount of
momentum stays the
same
3. When objects can collide and stick togetherthey will move as one object
a. The combined objects move in the direction of the
object that had greater momentum
b. They now have a combined mass of the 2 objects
c. Because they have a new mass (combined) they
have a new velocity also
d. Ex: Football players tackling
4. Objects can bounce off of each other in
collisions and the momentum is transferred from
one object to another
https://youtu.be/msaPn3TlG_E
a. Transfer of momentum causes the objects to
move in different directions at different speeds
BUT the total momentum stays the same
b. Ex; Bumper cars, bowling ball hitting pins
5. Conservation of momentum is explained by
Newton’s 3rd Law of motion
a. An object will hit another object with a force (action
force)
b. The object hit will exert a reaction force equal and
opposite to the action force
c. Ex: playing pool= the cue ball hits the billiard ball
causing the billiard ball to move and the cue ball to
stop
d. Bunting a baseball https://youtu.be/Gap1IthRcbg
CATAPULTS
1. Catapults work just like third
class levers
a.
b.
c.
d.
e.
The base of the catapult acts as
the fulcrum which the catapult
arm pivots on
The force is provided by tension
in rubber bands which are
attached to the crossbar of the
catapult
When the arm is pulled back,
the rubber bands tighten, so
when the arm is released, the
arm propels forward until it his
the crossbar
The load acts as the projectile in
the bucket
When the arm hits the crossbar,
the projectile leaves the bucket
and launches forward.
2. Newton's first law which
states that objects in
motion want to stay in
motion, likewise objects at
rest want to stay at rest
a. The projectile is moving at
the same speed as the arm
and the bucket
b. When the arm and bucket
stop, the projectile
continues to move forward
at the same velocity it was
before
c. Gravity brings the projectile
back to the ground which
gives it its trajectory.