# Chapter P4 - Explaining Motion

## Overview

• Describing motion - speed, velocity, acceleration, distance-time graphs, speed-time graphs; displacement-time graphs, velocity-time graphs.
• Forces - Newton's laws, interaction pairs, resultant forces, how forces affect motion, momentum
• Work and energy - work done, gravitational potential energy, kinetic energy

## Measuring Speed and Distance Time Graphs

• Click here for my some excellent powerpoints on forces and motion from Staffordshire Learning Net.
• Click here for PheT's Moving Man simulation - to explore displacement-time and velocity-time graphs.

## Newton's Three Laws of Motion

1. An object will not accelerate (speed up, slow down or change direction) if there is NO resultant force on it.
2. If an object experiences a resultant force, then it accelerates - its acceleration is proportional to the force and inversely proportional to the mass of the object.
3. Forces come in pairs - if A exerts a force on B in one direction, then B exerts a force on A in the opposite direction; the force is the same size and the same type.

## Physics Tracker Software

Click here to download "Physics Tracker" software. I use this to analyse regular and high speed video of experiments we do in class. 