Transcript force - Nutley Schools

Forces & Motion Notes
 Lesson 2: The Force of Gravity
 Lesson 3: The Force of A Rubber Band
(Elastic Force)
 Lesson 4: The Force of Friction
Lesson 2:
The Force of Gravity
Matter-
anything that has mass & takes up space
Massthe amount of matter in an object
Weightthe measure of the force of gravity
acting on an object
Gravity
 Gravity is a force that pulls objects toward each other
 The force of gravity acts between all objects on earth
and in the universe
 Earth’s gravity pulls everything towards its center
Forces are measured in Newtons
• The weight of an apple is about 1 Newton.
• The weight of a bag of sugar is 10 Newtons.
Mass
Weight
Always remains constant
Changes if gravity changes
Does not depend on gravity
Depends on gravity
Measured in grams (g) or
kilograms (kg)
Measured in Newtons (N)
Lesson 3:
The Force of A Rubber Band
(Elastic Force)
8
Stetching
hold
hold
Pull
Pull harder
Stop pulling and ---
9
• Elastic materials spring back into shape.
• Plastic materials stay stretched.
Elastic Forces
• A type of matter is considered to be elastic if
returns to its original shape after being squeezed
or stretched.
• Examples of Elastic Matter:
•
•
•
Types of Elastic Forces
There are two types of elastic forces: tension and compression
TENSION
COMPRESSION
An elastic force that
stretches or pulls matter
An elastic force that squeezes
or pushes matter together
Example:
Example:
Large cables that hold up a
bridge exert an upward force of
tension
on the bridge
When a person sits on a sofa
cushion, the cushion exerts an
upward force of compression
that holds the person up.
Tension
Compression
Placing a stent in an artery
1. The squeezed stent is placed at the blockage.
2. A balloon opens the stent.
3. The stent keeps the artery open so the blood can flow.
Step
1
Step
2
Step
3
Forces can do
amazing things!
Science saves lives
Lesson 4:
The Force of Friction
Friction
• Friction is a force that two surfaces exert on each other when
they rub against each other.
• Friction is a force that acts in the opposite direction to the
motion of an object.
Types of Friction
Sliding Friction 2 solid surfaces slide
over each other
Rolling Friction An object rolls across
a surface
Fluid Friction
Solid object moves
through a fluid
Static Friction Acts on objects that
are not moving
Drag= another word for air friction
THE END