1. What is a Force? A push or pull that Start movement Stop movement
Change the direction of movement
Cause an object in motion to speed up or slow down

2. 5 N 5 N Measuring Force Is written with Measured Magnitude ( a number)
Units (Newtons or N)
Direction (N, S, E, or W)
Measured
Using arrows
Using magnitude, units, and direction
Or Both
5 N
1 N = pounds (roughly 1/4 pound)
Have students determine their approximate weight in newtons to reinforce the size of the unit. When talking about problems, use both units to help them become more comfortable. For example, a N car is about a 2500 lb car.

3. Forces Contact forces Non-contact forces (Field forces)
Pushes or pulls requiring physical contact between the objects
Baseball and bat
Non-contact forces (Field forces)
Objects create force fields that act on other objects.
Gravity, static electricity, magnetism
Pictured is a contact force, the bat and the ball, as well as a field force, the static electric field around charged balloon exerting a force on small pieces of paper. Ask students to identify other examples of contact forces.

4. Contact Forces Direct contact that pushes or pulls an object
We can apply forces to an object
Pictured is a contact force, the bat and the ball, as well as a field force, the static electric field around charged balloon exerting a force on small pieces of paper. Ask students to identify other examples of contact forces.

5. Contact Forces Friction is the force that opposes motion
Pictured is a contact force, the bat and the ball, as well as a field force, the static electric field around charged balloon exerting a force on small pieces of paper. Ask students to identify other examples of contact forces.

6. Friction Forces: are opposite the direction of motion
The effects of friction are felt more with:
heavier objects.
rougher surfaces.
High friction example: sandpaper
Low friction examples: ice, air hockey table
Pictured is a contact force, the bat and the ball, as well as a field force, the static electric field around charged balloon exerting a force on small pieces of paper. Ask students to identify other examples of contact forces.

7. Kinetic friction - friction between moving surfaces
The force of sliding friction is typically greater than the force of rolling friction.
This is why it’s easier to push things on wheels than to slide them along the floor.
Pictured is a contact force, the bat and the ball, as well as a field force, the static electric field around charged balloon exerting a force on small pieces of paper. Ask students to identify other examples of contact forces.

8. Friction Without friction, an object would continue in motion
Pictured is a contact force, the bat and the ball, as well as a field force, the static electric field around charged balloon exerting a force on small pieces of paper. Ask students to identify other examples of contact forces.

9. Friction
Friction between the tires and the road helps a car or bicycle come to a stop when you hit the brakes.
Pictured is a contact force, the bat and the ball, as well as a field force, the static electric field around charged balloon exerting a force on small pieces of paper. Ask students to identify other examples of contact forces.

10. Friction
The danger when the roads are icy is that there is less friction between the tires and the road, making stopping or changes in motion more difficult.
Pictured is a contact force, the bat and the ball, as well as a field force, the static electric field around charged balloon exerting a force on small pieces of paper. Ask students to identify other examples of contact forces.

11. Drag- the force that opposes motion
Difference between friction and drag is where it happens:
Airplanes are designed to reduce drag, or to be aerodynamic.
Pictured is a contact force, the bat and the ball, as well as a field force, the static electric field around charged balloon exerting a force on small pieces of paper. Ask students to identify other examples of contact forces.