Download TEKS 4B : investigate and describe applications of Newton`s laws

TEKS 4B : investigate and
describe applications of
Newton’s laws such as in
vehicle restrains, sports
activities, geological
processes and satellite orbits.
Demo 1
Crash Cart &
Rubber Stopper
Teacher instructions
1. Obtain Crash cart (from Physics teacher) and a
rubber stopper (from Chemistry teacher)
2. Put rubber stopper on back of cart. Push into a wall
and have students observer what happens to the
stopper (it will continue to move and fall into the cart)
3. Repeat above but secure the stopper to the cart with
a rubber band (this time the stopper will be held in
place by the rubber band)
4. Ask the students what they observed and why it
happened.
5. Ask the students to think of real life situations where
this concept is employed. (seat belts in cars, child
car seats, seat restraints on roller coasters, etc)
Demo 2
Balloon
Teacher instructions
1.
2.
3.
4.
Obtain a balloon.
Blow balloon up.
Release balloon.
Ask students what happened and why it
happened. (Balloon flew around the room
because the air was being forced out the
nozzle (action) and the balloon was pushed
forward (reaction))
5. Ask students for example in real life where
this is demonstrated. (rocket engine, jet
engine, kick-back when shooting a shotgun,
etc)
Demo 3
Soft foam ball
on a string
Teacher instructions
1. Obtain a soft spherical object (foam ball, Styrofoam
ball, etc.)
2. Attach a string to the object.
3. Swing the object in a circle above your head while
holding the string.
4. Ask the students to make observations. (the object is
moving in a circular path around your hand)
5. Ask the student what forces are being applied to the
object (centripetal force pulling on the string, gravity
pulling down, air resistance)
6. Ask the student what path the object will take if you
released it. (It will continue moving away from you in
a straight line)
Demo 4
Paper on a
Table
Teacher instructions
1. Place a sheet of paper flat on a table.
2. Place fingers on the right and left edge of the
paper and push hands together.
3. Ask the students what type of stress is being
applied to the paper (compression) and to
make observation about what happens. (the
paper will bow upward in the middle
(simulating mountain building)).
4. Ask students of real life situations where
stress is being put on the Earth’s surface and
the results. (earthquakes, mountain building)
Review of concepts
Fill in the supplied worksheet
with the appropriate information
from the presentation.
Teacher instructions
1.Hand out handout.
2.Run the Powerpoint on
Newton’s Law and have
the students fill in
information where
necessary
st
1
Newton’s Law of
Motion - an object in motion
will stay in motion and an
object at rest will stay at rest
unless an unbalanced force
acts upon it . (Also known
as the Law of Inertia)
Inertia - the tendency of an
object to resist any change in
motion; the object will remain in
motion unless an unbalanced
force acts upon it. The more
mass an object has, the greater
it’s inertia will be.
Which vehicle has more inertia?
Which would be harder to push?
Which would be easier to stop?
Observe
st
Newton’s 1 Law
in action on the
next two slides.
Newton’s Second Law of
Motion - a net force acting
on an object causes the
object to accelerate in the
direction of the force. (Also
known as the Law of
Acceleration)
Force Equation:
Force = mass x acceleration
or
f = ma
Units: mass (kg)
acceleration (m/s2)
force (kg m/s2) or Newtons (N)
Forces that come into play during
Newton’s 2nd Law
• Friction - the force that opposes motion between
two surfaces.
• Air Resistance – the force air exerts on a moving
object
• Gravity – a force exerted by every object on every
other object. (force depends on distance and mass
between objects. The greater the mass, the greater
the grav. force. The greater the distance, the less the
grav. force)
Observe how air
resistance cause
object to fall at
different rates on
the next slides.
Elephant and
feather with no air
resistance.
Elephant and feather
with air resistance.
Minimizing
air resistance
in real life.
Weight – the force of gravity
acting on the mass of the object.
f = (m) x (a)
f = weight
a = acceleration due to
2
gravity - 9.8 m/s
weight = (mass) x (9.8
2
m/s )
The mass of an object
doesn’t change no matter
where you are in the
universe but the weight of an
object depends on the
gravitational pull on that
object.
That is why your mass is the same on the
moon but your weight is less.
Acc. due to gravity on Earth = 9.8 m/s2
Acc. Due to gravity on the moon = 1.6 m/s2
Mass
Weight
Earth
Moon
100 kg
100 kg
980 N
160 N
Newton’s Third Law of
Motion – for every action
force there is an equal and
opposite reaction force.
(Also known as the Law
of Reciprocal Actions)
A
B
C
D
Which direction will the girl on the skateboard
move if she threw the basketball forward?
A
B
C
D
Due to Newton’s 3rd Law she will move backwards. For every
action (throwing the ball forward) there is an equal and
opposite reaction (skateboard moves back)
Other situation
where Newton’s
rd
3 Law come into
play.
Other situations
where Newton’s
Laws are
demonstrated in
real life.
As magma is forced up through the
Earth’s crust it forces the rocks in place
to move aside to make room for it.
Earth’s internal forces are constantly
changing the Earth’s crust.
Newton’s Law
affecting the orbit
of planets and
satellites.
There is a balance
between the gravitation
pull of the center object
(sun) and the centripetal
force on the orbiting
objects (planets).
The smaller the mass, the smaller the
centripetal force (red vector) you will
have to apply to the rope.
The smaller the velocity of the object,
the less centripetal force you will have
to apply.
The smaller the length of rope (radius), the more
centripetal force you will have to apply to the
rope. (inner planets move faster because the
gravitational pull of the sun is greater)
If you let go of the rope (or the rope
breaks) the object will no longer be
kept in that circular path and it will be
free to fly off on a tangent.
Use your notes over
Newton’s 3 Laws of
Motion to answer the
following questions.
1. Name 3 forces
that comes into
play with Newton’s
nd
2 Law.
2. What is the
relationship
between mass
and inertia?
3. What is
another name
for Newton’s
nd
2 Law?
4. What would the weight of
a person who has a mass of
100 kg be (in N) on Mars?
Acceleration due to gravity
2
on Mars if 3.7 m/s .
5. Which of Newton’s Law is
being displayed in this
animation?
6. When the space shuttle
lifts off the engines are
putting out 6 million pounds
of thrust. Which of
Newton’s 3 Law is being
demonstrated by the lifting
off of the shuttle?
7. What is the relationship between
mass and centripetal force?
8. What force is being minimized in this
picture?
9. During an earthquake the Earth’s
crust is put under 3 types of stress.
(Tension, compression and shearing)
The result of this stress is movement of
the crust. Which of Newton’s 3 Laws
applies to this situation?
  tension
  compression
Shearing
10. If each of these objects were moving at
the same speed, which one would have the
most inertia?
A
B
C
D
Answer Key
1. Friction, air resistance,
gravity
2. As mass increases,
inertia increases
3. Law of Acceleration
4. 370 N
5. Newton’s 1st Law
• 6. Newton’s 3rd Law
• 7. The larger the mass,
the larger the centripetal
force
• 8. Air Resistance
• 9. Newton’s 3rd Law
• 10. B