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

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!

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

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!

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.

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!

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!

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)

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

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.

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.

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.

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)

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

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