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Transcript
```MAY THE FORCE
BE WITH YOU…
What is a force?
FORCE = Any push or pull which causes
something to move or change its speed or
direction
BALANCED VS.
UNBALANCED FORCES
Balanced forces are equal in size and
opposite in direction. There is NO motion.
Unbalanced forces are not equal in size
and/or opposite in direction. If the forces
on an object are UNBALANCED, we say a
NET force results. They change the speed
and /or direction of an object.
BALANCED FORCES
• If forces on an
object ARE equal in
size, the object will
not move or change
speed.
• When forces ARE
equal, the object will
not change direction.
UNBALANCED FORCES
• If forces on an
object ARE NOT
equal, the object
can move or
change speed.
• When forces ARE NOT
equal, the object can
change direction.
GIVE EXAMPLES OF
FORCES
Balanced Forces?
Unbalanced Forces?
ENERGY AND MOTION
• Mechanical energy is the energy an object
has because of motion or its position.
• There are two kinds of mechanical energy:
potential and kinetic.
Potential Energy
Potential energy is energy an object has
because of its mass or position.
This cat has potential
energy because of his
mass and height above
the ground.
How could we increase the
cat’s potential energy?
Kinetic Energy
Kinetic energy is the energy an object has
because it is moving.
The greater the speed and the
mass of the object, the greater
its kinetic energy.
WHAT IS MOTION?
A change in position of an object compared to a
reference point.
Motion involves all of the following: speed,
velocity, acceleration, and de-acceleration.
WHAT IS SPEED?
The rate of change in
position
Speed = distance ÷ time
WHAT IS VELOCITY?
Speed plus direction
Example: 50 km/hour north
WHAT IS ACCELERATION?
The rate of change in
velocity.
Positive acceleration = speeding up
Negative acceleration = slowing down
(decelerate)
WHAT IS GRAVITY?
The force of attraction
between objects that have
mass.
All objects have mass, so gravity
acts on all objects. Greater mass =
stronger force of gravity.
Why is the gravity on earth more than gravity on the
WHAT IS FRICTION?
The force that opposes
motion between two surfaces
in contact with each other.
together, air slowing down a
floating feather, water slowing
down a boat.
WHAT IS INERTIA?
The tendency of a body to
resist a change in motion.
An object at rest stays at rest.
An object in motion stays in
motion…unless acted on by an outside
force.
Speed is the distance traveled in a unit of time. Velocity
is speed in a direction.
Speed is how fast an object is moving.
Speed = distance
time
Your Turn! : Calculate the speed of the toy car over a
distance of 2 meters.
The graph
shows the
movement of a
car over time.
What is the car’s
average speed?
A.10 km/hr
B. 15 km/hr
C. 30 km/hr
D. 60 km/hr
A foam dart is thrown toward a dartboard. The graph
represents its motion. At about what speed is the dart traveling
when it hits the dartboard at 3 meters from the starting point?
A.7.0 m/s
B.8.5 m/s
C.8. 75 m/s
D.9.0 m/s
SOURCES
• http://www.openclipart.org/detail/38293
• http://carpictures.cc/cars/photo/car_model/24574/BM
W_F3
• http://ritter.tea.state.tx.us/student.assessment/resource
s/online/2009/taks_g08_science/8Science.htm