1. Section 2.1 Forces change motion
Mrs. Leos
Eighth Grade Science

2. Forces A push or a pull Three types Contact Force Gravity Friction
When objects use force by pushing or pulling an object.
Gravity
Friction

3. Vectors A quantity that measures both size and direction
Force is a vector
Direction of arrow is direction of force
Size of arrow is size of force (bigger arrow = more force, smaller arrow = less force)
What other kind of vector have you already learned about?

4. Net Force
Overall force acting on an object when all the forces are combined.
Total force that affects an object when multiple forces are combined.
The net force depends on both the direction and the size of individual forces.

5. Unbalanced Forces Balanced Forces Object does not move No net force
Same effect as no force
Also act on object moving in straight line with constant velocity
Object moves
Net force in one direction
One force on an object is greater than another

6. Measuring Net Force Identify forces to combine.
Put tail of second force arrow to tip of first. Maintain size and direction
Measure from tail of first arrow to tip of second force arrow.

7. Combining forces in opposite directions

8. Combining forces in the same direction

9. Newton’s First Law
Objects at rest remain at rest, and objects in motion remain in motion with the same velocity, unless acted upon by an unbalanced force
Objects with no net force acting on them have either constant velocity or zero velocity
Force is needed to start, change, or stop motion

10. Inertia Resistance of an object to a change in motion
Directly related to an object’s mass