# Chapter 2-Forces

by Melissa Schultz
# 1. Vectors

## 1.1. magnitude and direction

## 1.2. can be used to find net force

## 1.3. Examples: weight, velocity, force

## 1.4. measured using two methods

### 1.4.1. Polar method: descriptive, vector arrow with angle to horizontal

### 1.4.2. Step method: x hat and y hat, make triangle of x and y components, use SOH CAH TOA

## 1.5. arrows drawn tip to tail

# 2. Measurements

## 2.1. Newtons = kg * m/s^2

## 2.2. Weight = mass * gravitational field strength

## 2.3. mass = kg

## 2.4. average g (gravitational field strength) on earth = 9.80 N/kg

# 3. Newton's Laws

## 3.1. 1. Inertia - object moves until forces change its movement, or at rest till forces move it

### 3.1.1. Equilibrium

3.1.1.1. moving at constant speed and direction

3.1.1.2. staying at rest

## 3.2. 2. Force vector = mass scalar * acceleration vector

## 3.3. 3. For every action, there is an equal and opposite reaction; within an interaction pair of 2 objects

### 3.3.1. Internal forces

### 3.3.2. External forces

# 4. Field Forces

## 4.1. Gravitational

### 4.1.1. Newton's Law: any two objects exert gravitational forces on each other that are related to distance and mass

4.1.1.1. F = G*m1*m2 / r^2

4.1.1.2. G = universal gravitational constant

## 4.2. Electromagnetic

## 4.3. Strong

## 4.4. Weak

# 5. Contact Forces

## 5.1. Normal

## 5.2. Friction

### 5.2.1. Kinetic

### 5.2.2. Static

## 5.3. Tension

### 5.3.1. ideal pulley or cord

### 5.3.2. typically studied in biomechanics

# 6. Free Body Diagrams: show all forces on object

## 6.1. can be drawn and measured using vectors

# 7. Lab

## 7.1. Distance and time

## 7.2. Velocity and time

# 8. Blogs

## 8.1. Hurricane forces

## 8.2. Earthquake forces