# Chapter 9: Motion and Forces

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Chapter 9: Motion and Forces
Section 1: Describing Motion Motion Reference point Distance Displacement Vector Section 2: Speed and Velocity Speed Average speed Instantaneous speed Velocity Slope

Chapter 9: Motion and Forces
Section 3: Acceleration Section 4: Energy Work Kinetic energy Potential energy Gravitational potential energy Elastic potential energy Mechanical energy Law of conservation of energy

Describing Motion Motion happens when the distance from one object to another changes.

Describing Motion A Reference Point is a place or object used for comparison to determine if something is moving Motion is different for different reference points The choice of reference point determines an object’s relative motion.

Describing Motion Displacement is the length and direction that an object has moved from its starting point. Distance is the total length of the path between two points. Displacement is a vector, which is a quantity that has both magnitude (size) and direction.

Examples of Relative Motion
#1 Train is moving 100kph relative to the tree/earth Passenger is running 15kph towards the back of the train. How fast is the runner moving toward the tree? Direction of passenger Tree Direction of Train

Examples of Relative Motion
#2 Train is moving 100kph relative to the tree/earth Passenger is running 20kph towards the front of the train. How fast is the runner moving toward the tree? Direction of passenger Tree Direction of Train

Examples of Relative Motion
#3 Train is moving 10kph relative to the tree/earth Passenger is running 20kph towards the front of the train. How fast is the runner moving from the tree? Direction of passenger Tree Direction of Train

Examples of Relative Motion
#4 Train is moving 10kph relative to the tree/earth Passenger is running 10kph towards the back of the train. How fast is the runner moving toward the tree? Direction of passenger Tree Direction of Train