Download Force and Motion

Bellringer
• Get out essentials and turn to homework
• Read article on your desk forces
• Write questions and answers in isn
Force and
Motion
Day 1
Motion, force, and mass
Standard: 8-5
The student will demonstrate
an understanding of the
effects of forces on the
motion of an object.
(Physical Science)
• 8-5.4 Predict how varying the amount
of force or mass will affect the motion
of an object
Motion
• What is motion?
– A change in the position of an
object over time.
• How do you know something
has moved?
– You use a reference point!
• A stationary (not moving) object
such as a tree, street sign, or a
line on the road.
Did the
beaver
move?
• What causes an object to move?
– A FORCE!
– ALL motion is due to forces acting on
objects!
• What is a force?
– A push or a pull
MOTION
The total combination of the
forces acting on an object is
called NET FORCE.
YES!
Example: Gravity is pulling
you down to Earth, the
ground is supporting
you, and your legs
moving you forward as
you run during PE.
Can more than
one force act on
an object at the
same time?
#3
#1
#2
Mass
• Mass is how much matter is in something.
– You can physically touch matter.
– The more matter there is, the more something will weigh.
– It is not the same as weight -amount of gravity pulling on an
object.
• It’s harder to make a large object move or change the
speed and direction of it when it’s moving.
Questions
• What happens when I throw a baseball
and a bowling ball with the same force?
• Which one speeds up faster and why?
Lab: Motion After a Collision
p443 in text book
• How is it possible for a 70-kg football player to knock down
a 110-kg player? The smaller player usually must be running
faster. Mass makes a difference when two objects collide,
but the speed of the objects also matters. Explore the
behavior of colliding objects in this lab.
Lab Directions:
Space yourself about 6 feet away from a partner.
1. Slowly roll a tennis ball on the floor toward your
partner. Have your partner roll a tennis ball quickly
into the tennis ball. What happens?
2. Slowly roll a base ball on the floor toward your
partner. Have your partner roll a base ball quickly
into the tennis ball. What happens?
3. Roll one tennis ball and the other student roll to hit
the tennis ball with your ball what happened to both
tennis balls
4. Roll the base ball and hit it with the tennis ball and
record what happens
Lab: Findings
• What happened when you rolled the fast
moving tennis ball into the slow moving
tennis ball?
• What happened when you rolled the fast
moving baseball into the slow moving
tennis ball?
• What happened when you rolled two
tennis balls into each other at the same
speed?
Force and
Motion
Day 2
Force, mass and motion
Force Review
• If an object is in motion and more force is
applied to it, the object will begin moving
faster.
• If two objects have the same mass and a
greater force is applied to one of the objects,
the object which receives the greater force
will change speeds more quickly.
– Example – hit a ball harder it speeds up
Force Review
• If an object must be slowed down
quickly, the force applied to the object
must be greater than what is needed
for a gradual slowing down.
– Example: bicycle brakes
Force Review
• Varying the amount of force applied to a
moving object can also change the direction
that the object is moving more or less quickly.
– Example – baseball will change direction when hit
by a bat
Mass Review
• If a heavy (more massive) object is in motion,
more force must be applied to get the object
moving faster.
• If the same force is applied to two objects,
the object with the smaller mass will change
speeds more quickly.
– For example if a baseball and a bowling ball are
thrown with the same force the baseball will speed
up faster.
Mass Review
• In order to slow down or stop a heavier (more
massive) object, the force on that object
must be greater than for a less massive
object.
– Example – a small car will slow down more quickly
than a large truck
• It is more difficult to change the direction of
a heavy moving object, than one that is
lighter in mass.
.
The amount of matter
in an object
How much force gravity
pulls on an object
Weight depends on
location of object
Newtons (N)
scale
Yes on Earth once you leave
Earth your weight
will change, but
your mass will
remain the same
Always constant (same)
no matter the location.
g, kg, mg
Balance
Lab: marble Forces and Motion
page 471
• Lean 2 meter sticks parallel, less than a marble width
apart on 3 stacked books. This is your ramp.
• Tap a marble so it rolls up the ramp. Measure how far
up the ramp it travels before rolling back.
• Repeat step 2 using 2 books, 1 book, 0 books. The
same person should tap with the same force each
time.
• Make a table to record the motion of the marble for
each ramp height.
Forces and Motion Lab
Marble Roll Height
40
35
I
N 30
C
H 25
E
S 20
Marble
15
10
5
0
3 Books
2 Books
1 Book
Number of Books Stacked
0 Books
Question
• What would happen if the ramp were
perfectly smooth and level?
Exit Slip
• Explain how changes in mass effect the
motion of an object.
Force and
Motion
Day 3
Force, mass and motion review
Balanced and Unbalanced forces
Review
• True or False
If an object is in motion and more force is
applied to it, the object will begin moving
faster.
True or False
• If an object must be slowed down
quickly, the force applied to the object
must be greater than what is needed
for gradual slowing down or stop
Mass
• If a heavy (more massive) object is in
motion, more force must be applied to
get the object
moving______________.
(Faster/slower)
True or False
• It is more difficult to change the
direction of a heavy moving object, than
one that is lighter in mass.
Indicator:
• 8-5.5 Analyze the resulting effect of
balanced and unbalanced forces on an
object’s motion in terms of magnitude
and direction.
Balanced Forces
• A balanced force is one in which the net
force equals ZERO.
• Do you think there will be any motion?
– NO!
• Examples:
25 Newtons
25 Newtons
Unbalanced Forces
• An unbalanced force is one in which the
net force is greater than zero.
• Do you think there will be any motion?
– YES!
• Examples:
50
N
25 Newtons
40 Newtons
2 N
Only an _______________
force can change the motion
of an object.
• Example: Your dog
can cause you to
move if he pulls
with enough force.
– His force is greater than
the force you’re using to
stay in place
What would happen if an
unbalanced force acted on an
object that’s already in motion?
• It will change the
speed or direction
of the object.
• Example: Your little
brother is riding his
tricycle. You run up
behind him and give
him a push.
– Your force adds to the
existing force causing
him to speed up.
Unbalanced forces can act in
the same direction.
• Example: You’re pushing a cabinet across
the room with a force of 15 N. You’re
friend is pulling with a force of 10 N.
• What is the NET FORCE?
• What direction is the cabinet moving?
15 Newtons
10 Newtons
Unbalanced forces can act in
opposite directions.
• Example: Two dogs are tugging on a rope.
One dog pulls with a force of 20N and the
other pulls with a force of 25N.
• What is the NET FORCE?
• What direction is the rope moving?
20 Newtons
25 Newtons