Unit 2, Lesson 7
Constant Speed
Accelerated 6
Preparation
Lesson Narrative
This lesson introduces the context of constant speed. Through concrete experiences, students continue to explore equivalent ratios and ratios involving 1 unit. They measure the time it takes them to travel a predetermined distance moving slowly and then quickly—and use it to calculate and compare the speed they traveled in meters per second.
Here, double number lines are used to represent the association between distance and time, and to convey the idea of constant speed as a set of equivalent ratios. (For instance, 10 meters traveled in 20 seconds at a constant speed means that 0.5 meter is traveled in 1 second, and 5 meters are traveled in 10 seconds). Students come to understand that, like price, speed can be described using the terms per and at this rate.
Students reason quantitatively and abstractly (MP2) as they think about constant speed as a measure that relates two quantities—distance and time. The idea of constant speed will be foundational for understanding constant rate, an even more abstract idea introduced later.
- Calculate the distance that an object travels in 1 unit of time and express it using a phrase like “meters per second” (orally and in writing).
- For an object moving at a constant speed, use a double number line diagram to represent equivalent ratios between the distance traveled and elapsed time.
- Justify (orally and in writing) which of two objects is moving faster, by identifying that it travels more distance in the same amount of time or that it travels the same distance in less time.
Let’s use ratios to work with how fast things move.
Required Materials
Required Preparation
Set up 4 paths as shown in the diagram, with a 1-meter warm-up zone and a 10-meter measuring zone. Mark the beginning of the warm-up zone, the start line, and the finish line.
A diagram of a line with three markings. The first mark is labeled "Warm-up Mark", the second mark is labeled "Start", and the third mark is labeled "Finish". The distance between the first and second mark is labeled 1m. The distance between the second and third mark is labeled 10m.