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Worksheet Grade 8 Math

Sedgebarrow Road Fire Flow Test: Matching Graphs to Events

A grade 8 worksheet where students sketch and describe pressure and flow graphs for a fictional fire flow test, matching each graph shape to what the crew did.

Objectives

  1. Students will sketch a graph that matches a written description of pressure changing over time.
  2. Students will describe in words what a given graph says about a hydrant test.
  3. Students will compare the steepness of two parts of a graph and explain what the difference means.

Vocabulary

Key words: increasing, decreasing, constant, steepness

Teacher overview

Before a new building goes up, a crew runs a fire flow test on the nearest hydrants to find out how much water the mains can deliver, and a gauge records the pressure the whole time. The record is a graph with a very readable shape: level while nothing is open, falling while hydrants run, level again while the test holds, and rising back once the hydrants close. This worksheet uses a fictional test on Sedgebarrow Road, and it asks for graph shapes rather than numbers, so students practice reading a graph qualitatively rather than calculating from it.

Sedgebarrow Road Fire Flow Test: Matching Graphs to Events — Grade 8 Math
Name: ____________________________ Date: ______________

Student Worksheet

A crew ran a fire flow test on Sedgebarrow Road in the fictional town of Larksmere. On every graph below, time runs across the bottom and pressure runs up the side. No numbers are needed. Draw smooth lines and label each part of every sketch.

  1. Sketch a pressure graph for this test. The pressure holds level for 10 minutes. One hydrant then opens and the pressure drops quickly. It stays low for 5 minutes. The hydrant closes and the pressure climbs back to where it started.
  2. A second graph falls in two steps, with a short level stretch between the two drops. Describe what the crew did during that time.
  3. The crew opens one hydrant on one test and three hydrants at once on another test. Which test makes the steeper drop on the pressure graph? Explain.
  4. On one graph the line is flat for 6 minutes while a hydrant is still running. What does that flat part say about the pressure?
  5. Sketch a pressure graph for a test in which the pressure never returns to its starting level after the hydrant closes. Then give one reason that could happen.
  6. On one graph the pressure climbs slowly for 20 minutes after the last hydrant closes, instead of jumping straight back up. Describe what that slow climb says about the system.
  7. Sketch a second graph for the test in item 1, but this time put the flow out of the hydrant up the side instead of pressure. Show flow before the hydrant opens, while it runs, and after it closes.
  8. Compare your two sketches from items 1 and 7. When the pressure graph goes down, what does the flow graph do?
  9. A student draws the pressure drop as a straight up-and-down line. Explain why the real graph cannot be perfectly vertical.
  10. Describe in words the story told by this graph: level, then a slow fall for 15 minutes, then a sharp fall, then level for 5 minutes, then a quick rise back to the start.

From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.

Answer Key
  1. Answer: A graph with four parts in order: a flat stretch, a steep fall, a shorter flat stretch at a lower level, and a rise back to the first level. Accept any sketch with those four parts in that order and with the last level matching the first.
  2. Answer: The crew opened one hydrant, waited while the pressure settled, and then opened a second hydrant. Each opening pulls more water from the main, so each one drops the pressure again.
  3. Answer: The test with three hydrants. Three open hydrants pull much more water at once, so the pressure falls further in the same amount of time, which makes a steeper line.
  4. Answer: The pressure is staying the same. Water is still flowing out of the hydrant, but the mains are delivering it as fast as the hydrant releases it, so the level holds steady.
  5. Answer: A graph that falls, holds low, then rises to a level below the starting line. A reason could be that a valve was left partly closed after the test, or that the storage tank had not yet refilled when the reading was taken.
  6. Answer: The system is refilling slowly. Pumps and storage are putting water back into the mains, but not fast enough to restore the pressure at once, so the recovery is gradual rather than sudden.
  7. Answer: A flow graph with three parts: flat at zero before the hydrant opens, a jump up to a steady level while it runs, and a drop back to zero when it closes. Accept any sketch showing zero flow at the start and end and a constant flow in the middle.
  8. Answer: The flow graph goes up. Opening the hydrant sends water out, which raises the flow and lowers the pressure at the same moment, so the two graphs move in opposite directions.
  9. Answer: A vertical line would mean the pressure had two different values at the same instant, which cannot happen, and it would also mean the change took no time at all. The drop is fast but it still takes a few seconds, so the line is steep rather than vertical.
  10. Answer: The pressure sits steady, then something starts drawing a small amount of extra water for 15 minutes, then a hydrant opens and the pressure drops sharply. The pressure then holds at that low level for 5 minutes while the hydrant runs, and the hydrant closes and the pressure returns quickly to where it began.

Differentiation

Support

Give these students three pre-cut graph segments, one rising, one flat, and one falling, that they can arrange and trace to build each sketch. Reduce the required set to items 1, 3, 4, and 7, and provide the labels "hydrant opens" and "hydrant closes" as stickers to place on the sketch.

Extension

Ask students to sketch a single graph for a test on a street where two hydrants open at different times and close at different times, then write a paragraph explaining which drop is steeper and which recovery is faster. Have them mark the point on the graph where the mains were working hardest.

ELL supports

Pair each vocabulary word with a hand motion, using a rising hand for increasing, a flat hand for constant, and a lowering hand for decreasing. Provide the sentence frames "The pressure goes ___ because ___" and "This part of the graph is flat, so the pressure is ___."

Extensions

Have students find the shape of a graph for a very different water event, such as a tank refilling overnight, and write a short description that a classmate could use to redraw the graph without seeing it.