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# Forces

## Newton's Laws

### 1st Law

The Law of Inertia, An object's velocity does not change if and only if the net force acting on the object is zero. (page 29)

F=ma

more in Ch. 3

### 3rd Law

Interaction Pairs, interaction between two objects will exert force on the other., Internal interactions, add up to zero, both interacting objects are part of the system, External interactions, only one of the two onjects are part of the system, These forces are equal inmagnitude and opposite in direction, Gravitational Forces

## Different Types

### Long range Forces

Gravity, gravity of the planets is an example

Weight

Do not require forces to touch

### Normal forces

A contact force perpendicular to the contact surface that prevents two objects from passing through one another

a book sitting on a table is an example

equal

### Contact Forces

A force exerted on another force.

The Contact force only last as long as the objects are touching.

### Equilibrium

conveys the idea that the forces are in balance

The net force is zero

### Fundamental forces

Electromagnetism, field is unlimited, electrical charge, stronger than gravitational force

Gravitational Forces, Newton's laws of gravitational forces

The strong force, holds protons and neutrons together, The strongest of all forces

The weak force, radioactive decay process

### Interactions

Internal, Both objects are interacting on the system

External, When only one object is interacting on the system

## Vectors

### Magnitude

the speed at which the objects moves

### Direction

direction of motion

always physical direction in space

### Quantities

Scalar, Mass, has magnitude, algebraic sign, and units but no direction in space, Temperature

## Problem Solving

### Net Force

Vector sum of all the forces acting on an object

### Free Body Diagrams

Simplified sketch

A single object with all the force vectors acting on that object

Tail to tip method

Finding components of a vector, draw right triangles, equations, add all the components, Sin/Cos/Tan

## Friction

### Static Friction

acts on objects to prevent them from moving, A car stopped on a hill, a bathroom mat in the shower

### Kinectic Friction

when two objects are slipping and sliding across one another, Earth plates

acts on the object to get it to stop

## Tension

### pulls on an object in opposite directions

a chandelier hanging from the ceiling, A force hanging it up (the cord), the force of gravity pulling it down

### Tensile forces

Body, biomechanics, tendons/muscles, bones

### Pulleys

ideal pulleys, no mass, no friction, can change the direction of the force exerted on an object, does not change magnitude, chains/chords/cables

## Words of the Day

### Ramp-up

build up and strengthen skills in physics

### Chains

tension forces and gravity