Transcript Newton's Laws powerpoint - South Webster High School

Forces and Motion
PS9.21
PS9.22
PS9.23
PS9.24
ps9.25
Forces can create changes in
motion 3 types of
acceleration (change in
speed or direction
 (acceleration) speeding up
 Deceleration is negative
acceleration or slowing down
 Centripetal acceleration
changing direction
Motion can be described as
a
change in an
object’s position
 Average velocity
(speed) is the
change of position
of an object over
time
Velocity Graphs
V = distance
time
Velocity
(v) is
the slope (rise
over run) of a
position (d) vs.
time (t) graph
Distance (m)
 Velocity
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40
Series1
20
Series2
0
1 3 5 7 9 11 13 15
Time (sec)
40 The diagram represents the total travel of a
teacher on a Saturday. Which part of the trip is
made at the greatest average speed?
FQ
How do we work this one?
GR
Calculate v = d/t for each segment.
HS
J T
Acceleration Graphs
 Acceleration
Acceleration
Velocity ((m/s)(m)
(a)
is the slope of a
velocity (v) vs.
time (t) graph
 Plotted on a
distance vs. time
graph,
acceleration is an
exponential curve
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40
20
0
1
3
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Time (sec)
11
13
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Acceleration is a change in an
objects velocity (speed or
direction)
When an object’s
speed changes over
time it is accelerating
(or decelerating)
 A = vfinal – vinitial
time
 Units for acceleration
m/s/s or m/s2

Definition of a Force
A
Force is
a push or a
pull
Balanced Force
A
force that
produces no
change in an
object’s motion
because it is
balanced by an
equal, opposite
force.
Unbalanced
Forces
Are forces
that results
in an
object’s
motion
being
changed.
+
Friction
A force that acts in a
direction opposite to the
motion of two surfaces in
contact with each other.
Friction
Friction causes an
object to slow
down and stop.
Since the amount of
energy stays
constant, the
energy becomes
heat.
Newton’s 1st Law of
Motion
 Object
in
motion
stays in
motion
Newton’s 1st Law of
Motion
And
Objects
at rest
stay at
rest
Newton’s 1st Law of
Motion
 Until
they are acted upon
by unbalanced forces.
Inertia or Newtons 1st Law
Tendency for an
object to stay at
rest or moving in
a straight line at
a constant speed.
 The mass (m
measured in kg)
of an object
determines its
inertia

Newton’s 2nd
Law of Motion
Force = Mass X
Acceleration
F=ma
Weight (pull of gravity) is a
commonly measured force,
calculated by F=mg, g is the
acceleration due to gravity 9.8
m/s2
Newton’s 2nd Law of Motion
The greater the
mass of an
object, the
greater the
force required
to change its
motion.
Newton’s 2nd Law of Motion
 The
greater the
acceleration of
an object, the
greater the
force required
to change its
motion.
11 The frog leaps from its resting position at
the lake’s bank onto a lily pad. If the frog has
a mass of 0.5 kg and the acceleration of the
leap is 3 m/s2, what is the force the frog exerts
on the lake’s bank when leaping?




A 0.2 N
B 0.8 N
C 1.5 N
D 6.0 N
Formula chart says F=ma, m is mass
in kg, a is acceleration in m/s2.
So, .5 kg x 3 m/s2= 1.5 N
Newton’s 3rd Law of Motion
 For
every
action force
there is an
equal and
opposite
reaction
force.
Newton’s 3rd Law of Motion
All forces come
in actionreaction pairs
Ex: feet push
backward on floor,
the floor pushes
forward on feet
Universal Law of Gravitation
Between any
two objects in
space there is
gravity
Universal Law of
Gravitation
Gravity varies depending
on two factors:
1) the mass of the object
doing the pulling, and
2) the distance from the center
of that object
On Earth gravity = 9.8 m/s/s
For
every
second that an
object falls its
speed increases
by 9.8 m/s