# Unit 3 Review

## Learning Targets

1. 3-1. I can describe the ideal conditions applied to the study of forces (ignoring friction).
2. 3-2. I can diagram and calculate the horizontal and vertical components of force.
3. 3-3. I can explain contact forces on the atomic scale using the particle model.
4. 3-4. I can mathematically describe frictional forces.
5. 3-5. I can explain and calculate the apparent weight of an object when it’s acceleration is zero
6. 3-6. I can apply Newton’s first law of motion to mathematically describe and predict the effects of forces on complex systems of objects.

## Unit 3 Vocab

Vocabulary

1. component
2. equilibrium
3. free-body diagram
4. forces
5. applied
6. elastic
7. electrostatic
8. friction
9. gravitational
10. net
11. normal
12. tension
13. nuclear
14. inertia
15. system

## Newton's First Law

• "Law of Inertia"
• "An object at rest will stay at rest unless an outside force act's upon it"
• "An object will stay in motion unless an outside force acts upon it"
• Inertia is the tendency of an object to resist change in velocity.

## Force Concepts and Inertia

Force

• Can be push or pull
• Vector quantity, has direction
• Contact: touching

## Equilibrium

• No acceleration
• All forces are balanced
• Same magnitude and opposite direction

## Free Body Diagrams

• A diagram or model of forces
• Use vectors (arrows) to diagram forces
• Tails of arrows should be connected to other tails
• The object of interest should be labeled as a dot
• The length of the arrows show magnitude and provide direction of force

## Types of Forces

• Fg - Gravity
• Fn - Normal
• Fa - Applied
• Ff - Friction
• Fmag - Magnetic
• Ft - Tension
• Fnet - Net
• Fel - Elastic

## Formulas / Units / Symbols

• SOH-CAH-TOA
• Fnet = F1 + F2 … +Fn
• F2 = Fx2 + Fy2
• Newtons (N)
• 1 N = 1 kg * 1 m/s2