Motion and Force Chapter Twelve: Distance, Time, and Speed Chapter Thirteen: Forces Chapter Fourteen: Force and Motion

Chapter Twelve: Distance, Time, and Speed 12.1 Distance, Direction, and Position 12.2 Speed 12.3 Graphs of Motion

Investigation 12A How do scientists describe motion? Distance, Time, and Speed

12.2 Speed Speed is the most common measurement used to describe the motion of objects. Once you know an object’s speed, you can figure out how far it can go in a certain amount of time. You can also predict how long it will take to get somewhere.

12.2 Speed The speed of a bicycle is the distance it travels divided by the time it takes.

12.2 Velocity Speed with direction is called velocity.

12.2 Constant Velocity A plane with a constant velocity of 600 km/h west moves in a straight line. (Its speed and direction remain the same.) A car going around a bend at a constant 30 mph has a constant speed, but its velocity is not constant. (Note the change in direction.)

12.2 Average Speed The speed found by dividing the total distance by the total time is the average speed.

12.2 Relationships between distance, speed and time An equation can be used to calculate speed, distance, or time if two of the three values are known.

Activity Speed is how fast something moves in relation to a reference point without regard to the direction. In this activity you and a partner will each calculate your average speed in different units. How Fast are You?