1. Newton’s First Law of Motion
Ch. 2 Lesson 2
An object at rest stays at rest until acted upon by an outside force

2. The combination of all the forces action on an object
Net Force
The combination of all the forces action on an object
Just like the free-body diagrams we did!
The net force depends on the directions and magnitude of the forces applied to an object

3. Combining Forces in the Same Direction
When forces are applied in the same direction we add the forces together!

4. Combining Forces in the Opposite Directions
In this case you still sum the forces, but one is negative (moving against the other)
Ultimately you subtract!

5. Balanced Forces
Forces on an object that combine and forma net force of zero
The object doesn’t move!

6. Unbalanced Forces
Forces acting on an object that combine a form a net force that is not zero
Object Moves

7. Newton’s First Law of Motion
(book definition) If the net force on an object is zero, the motion of the object does not change
(Everyone else’s definition) An object in motion will stay in motion unless acted on by an outside force. An object at rest will stay at rest unless acted on by an outside force.

8. Balanced Forces and Motion
Balanced forces cause no change in the objects velocity
This is true when an object is at rest or in motion

9. Unbalanced Forces and Motion
Newton’s 1st Law only applies to balanced forces
When unbalanced forces act on an object at rest, the object starts moving
When unbalanced forces act on an already moving object, the object’s speed, direction, or both can change!

10. Inertia The tendency of an object to resist a change in motion
This basically describes Newton’s First Law of Motion – sometimes called the law of inertia

11. So Why Do Objects Stop Moving?
Static Friction and inertia prevent objects from moving initially
On Earth there is friction which slows and object and eventually stops it
In space, inertia keeps objects moving until acted upon by an outside force

12. Lesson 2 Review
Pg #1-9
Remember you have a quiz over friction and gravity (ch. 2 lesson 1) tomorrow!!!!