1. Day 4 12-2-10 Topic: Net Force; Intertia
Objective: I can resolve forces into x and y components, then find the net force
Science Starter: 1.) Draw & Label the force arrows 2. ) Why is the orange arrow longer? F
Normal / support
O’NEILL – GREAT WORK F F
friction
push F
gravity
Friction RESISTS motion

2. Agenda Teaching Table Cooperative Group H.W Quiz: Friday Net Force
Inertia
Cooperative Group
Force Challenge 3.1;
Q-V Collected for Grade
One Grade per Group
H.W
3.1 K-P
Quiz: Friday

3. Net force Zero? or Non-Zero?
Adding up forces can be different from simply adding numbers because the directions (vectors) of the forces matter.
For this reason the term net force is used to describe the total of all forces acting on an object.
When used this way, the word “net” means total but also implies that the direction of the forces has been taken into account when calculating the total.
Net Force = -4N
The ball moved in
(-) direction

4. Adding forces

5. Subtracting Forces

6. Total Net Force 1. Total Net Force= 2. Total Net Force=3.
1. Total Net Force=
2. Total Net Force=
3. Total Net Force=

7. What is Inertia?
Inertia: is the property of an object that resists changes in its motion.
Inertia comes from mass. Objects with more mass have more inertia and are more resistant to changes in their motion. Demo: Shot Put vs.Tennis Ball
Newton’s 1st Law:
An object at rest will stay at rest …
an object in motion will continue in motion with the same speed and direction unless acted on by an unbalance outside force.
Demo: Coin & Cup
Video: Table Cloth (Scilinks)

8. Simply put… Inertia is directly related to mass.
More mass more inertia!
Less mass less inertia!

9. Exit Ticket 1. State Newton’s first law in your own words.
2. How is mass related to inertia?
3. What is the net force and how is it determined?