1. 8 TH G RADE S CIENCE HERMON M IDDLE S CHOOL Force

2. Mass ● The amount of “stuff” in an object ● Closely related to weight / how “heavy” something is ● Measured in grams (g) ● Kilograms (kg), milligrams (mg), etc.

3. Inertia ● An object’s resistance to a change in motion ● Based on an object’s mass ● The more mass an object has (more massive), the more inertia it has ● This is what keeps the dishes on the table when the table cloth is yanked out from underneath ● Newton’s First Law: Objects at rest will stay at rest, and objects in motion will stay in motion, unless they are acted upon by an outside (unbalanced) force

4. Force ● Defined as a PUSH or a PULL ● Force (F) = Mass (m) * Acceleration (a) ● Balanced forces will not change an object’s motion ● Unbalanced forces will change an object’s motion ● Units for force are NEWTONS (N) ● 1 N = 1 (kg * m) ÷ s ² ● Newton’s Second Law states that F=ma

5. Nerdy Humor

6. Friction ● A force that occurs when surfaces touch (are in contact) ● Always OPPOSES (works against) motion ● If an object is moving, friction slows it down ● If an object is at rest, friction makes it more difficult to move

7. Static Friction ● Occurs between surfaces that are not moving (relative to each other) ● Friction that holds an object “still”

8. Sliding Friction

9. Rolling Friction

10. Fluid Friction ● Something moving across a “greased” surface ● Air hockey puck ● Ice skates ● Skis ● Challenge: name 2 examples of fluid friction that would be acting on the above ship

11. Gravity ● A property of all matter ● Similar to magnetism… BUT: ● VERY, VERY weak ● Only attracts, does not repel ● Related to an object’s MASS ● The more massive an object is, the more gravitational pull it has ● Why can we feel Earth’s gravity, but nothing else’s?