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
Mass-
the amount of matter in an object
Weight-
the measure of the force of gravity
acting on an object
GravityGravity 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.
Lesson 3:The Force of A Rubber Band
(Elastic Force)
8
Stetching
Pull
Pull harder
hold
hold
9
Stop pulling and ---
• 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 ForcesThere are two types of elastic forces: tension and compression
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 ENDTHE END