1. Topic: Force
PSSA: C/S8.C.3.1

2. Objective: TLW describe forces and how they act on objects.
TLW compare balanced and unbalanced forces.

3. MI #1: What is a Force?
A force is a push or a pull that gives energy to an object and sometimes changes the object’s motion.
The change in motion may be due to a change in speed or direction.

4. MI #2: Net Force
Net force is the combination of all the forces on an object.
Forces that act in the same direction add together, forces that act in opposite directions subtract from each other.

5. MI #3: Balanced vs. Unbalanced Forces
Balanced forces produce a net force of 0N, so a change in motion will not occur.
Unbalanced forces (net force > 0) produce a change in motion.

6. So What…Real Life Application
Understanding how forces act upon objects is necessary to understand why motion occurs.

7. Topic: Friction
PSSA: C/S8.C.3.1

8. Objective: TLW explain what friction is and how it affects motion.
TLW describe two types of friction.
TLW explain why friction can be both helpful and harmful.

9. MI #1: What is Friction?
Friction is a force that opposes motion between two surfaces; it causes a moving object to slow down and finally stop.
Friction occurs anytime two surfaces are touching, but the amount of friction depends on the force pushing the surfaces together and the roughness of the surfaces.

10. MI #2: Types of Friction
Static Friction – no motion takes place because the friction supplies the balanced force.
Kinetic Friction – the friction between moving surfaces.
There are three types of kinetic friction – sliding, rolling, and fluid.

11. MI #3: Ways to Increase and Reduce Friction
There are many reasons to increase friction…
Sand on roads, batting gloves, golf club grips, scouring pads.
There are many ways to reduce friction.
Lubricants, ball bearings, sanding, etc.

12. So What…Real Life Application
Understanding friction is important to understanding why moving objects slow down and stop, why objects wear down, why weathering of rocks takes place, etc.