1. 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

2. Lesson 2: The Force of Gravity

3. Words to Know
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

4. 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

5. Forces are measured in Newtons
The weight of an apple is about 1 Newton.
The weight of a bag of sugar is 10 Newtons.

6. 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)

7. Lesson 3: The Force of A Rubber Band (Elastic Force)

8. Stetching
hold
Pull
Pull harder
hold

9. Stop pulling and --- Elastic materials spring back into shape.
Plastic materials stay stretched.

10. 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:

11. 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:
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.

12. Tension
Compression

13. Placing a stent in an artery
The squeezed stent is placed at the blockage.
A balloon opens the stent.
The stent keeps the artery open so the blood can flow.
Step 1
Step 2
Step 3

14. Forces can do amazing things!
Science saves lives

15. Lesson 4: The Force of Friction

16. 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.

17. 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

18. Drag= another word for air friction

19. THE END