Unit 3: Motion, Forces, & Energy Chapter 9: Motion & Energy Big Idea: You can describe the motion of an object by its position, speed, direction, & acceleration

4 Sections Describing Motion Speed & Velocity Acceleration Energy Mrs. Lee - Ch 9

Sec 1: Describing Motion KEY CONCEPTS An object is in motion if it changes position relative to a reference point Distance is the total length of the actual path between 2 points. Displacement is the length & direction of a straight line between starting & ending points Mrs. Lee - Ch 9

Sec 1: Key Terms Motion Reference point Distance Displacement Vector Mrs. Lee - Ch 9

Sec 2: Speed & Velocity KEY CONCEPTS To calculate the speed of the object, divide the distance the object travels by the time it takes to travel that distance Speed = Distance Time Changes in velocity may be due to changes in speed, changes in direction, or both Mrs. Lee - Ch 9

Sec 2: Speed & Velocity (cont’d) The slope of a distance vs. time graph represents speed -- the rate that distance changes in relation to time Slope = Rise Run Mrs. Lee - Ch 9

Sec 2: Key Terms Speed Average speed Instantaneous speed Velocity Slope Mrs. Lee - Ch 9

Sec 3: Acceleration KEY CONCEPTS In science, acceleration refers to: 1) increasing speed 2) decreasing speed or 3) changing direction To determine the acceleration of an object, you must calculate its change in velocity per unit of time Mrs. Lee - Ch 9

Sec 3: Acceleration (cont’d) Acceleration = Final velocity – Initial Velocity Time You can use both a speed vs. time graph & a distance vs. time graph to analyze the motion of an accelerating object Mrs. Lee - Ch 9

Sec 3: Key Terms Acceleration Mrs. Lee - Ch 9

Sec 4: Energy KEY CONCEPTS The kinetic energy of an object depends on both its mass & its speed Kinetic Energy = 1 x Mass x Speed2 2 An object’s gravitational potential energy depends on its weight & on its height relative to a reference point Mrs. Lee - Ch 9

Sec 4: Energy (cont’d) Gravitational potential energy = Weight x Height Mechanical energy = Potential energy + Kinetic energy Mrs. Lee - Ch 9

Sec 4: Energy (cont’d) Any object that rises or falls experiences a change in its kinetic & gravitational potential energy According to the law of conservation of energy, energy cannot be created or destroyed Mrs. Lee - Ch 9

Sec 4: Key Terms Work Energy Kinetic energy Potential energy Gravitational potential energy Elastic potential energy Mechanical energy Law of conservation of energy Mrs. Lee - Ch 9