1. 8th Grade Science Mrs. Butsch
Physics Notes -Forces
8th Grade Science
Mrs. Butsch

2. Definition: Force A force is a push or a pull on an object.
Objects exert forces on each other.
EXAMPLE: When you sit on a chair, you exert a force on the chair and the chair exerts a force on you!

3. Newton's
Force is measured in units called Newton’s (N) Named after Sir Isaac Newton.

4. Types of Forces: Gravity
Gravity: is the force of attraction between objects that have mass.
ALL objects have mass so gravity acts on EVERYTHING on Earth!

5. Mass Mass: Is a measure of the amount of “stuff” in an object.
The greater the mass of either object, the stronger the gravity between them.

6. Types of Forces: Friction
Friction is the force that opposes motion between 2 surfaces that are in contact with each other.
Example: A car driving on a road in normal conditions vs. on ice!

7. Types of Forces: Centripetal Force
Centripetal Force is the force that caused objects to move in a circular path.
Example: The moon constantly revolves around, or circles, Earth. Gravity causes centripetal force!

8. Balanced and Unbalanced Forces
Net Force on an object is the combination of all the forces acting on it.
Forces in Same Direction
30 N to the left
20 N to the left
30 N (left) + 20 (left) N = 50 N (left)

9. Balanced and Unbalanced Forces
Forces in Opposite Directions
10 N to the left
8 N to the right
10 N (left) – 8 N (right) = 2 N to the left

10. Balanced and Unbalanced Forces
Balanced Forces occur when the total of all forces on an object equals Zero and the object’s motion does not change.

11. Balanced and Unbalanced Forces
Unbalanced Forces occur when the net force on an object does not equal zero; results in the object changing its motion.

12. Kinetic vs. Potential Energy
Kinetic Energy is energy an object or particle has because it is moving.
Potential Energy is stored energy an object has because of its position or shape.

13. Dealing with Newton’s Laws
Speed (S) is the distance traveled by an object in a given amount of time (t).
Example: A car traveling on the highway. Its speed is 70 mph.
Speed = Distance/ Time ( s= d/t)

14. Dealing with Newton’s Laws
Velocity (v) is an objects speed and direction at a given instant.
Velocity = Distance/ Time
V= d/t
Example: If a car is has traveled 100 miles in 2 hours, then V = 100 miles/ 2 hours
V= 50 miles/hour

15. Dealing with Newton’s Laws
Acceleration is the change in an object’s velocity over time.
Acceleration = Change in Velocity/Time
a = v/t