This deep dive covers Container Filling Graphs (Water Problems) within Real-Life Graphs for GCSE Mathematics. Revise Real-Life Graphs in Graphs for GCSE Mathematics with 14 exam-style questions and 12 flashcards. This is a high-frequency topic, so it is worth revising until the explanation feels precise and repeatable. It is section 4 of 10 in this topic. Use this deep dive to connect the idea to the wider topic before moving on to questions and flashcards.
Container Filling Graphs (Water Problems)
When water fills a container at a constant rate, the shape of the container determines the shape of the graph of depth against time.
- Cylinder (uniform width): straight line — depth increases at a constant rate
- Wider at the top: graph curves and becomes less steep as water spreads over a larger area
- Narrower at the top: graph curves and becomes steeper as the same flow fills a smaller cross-section faster
- Vase shape (wide-narrow-wide): graph is steep, then shallow, then steep again
Tip to remember: Imagine pouring water in. If the container gets wider, the depth rises more slowly (shallower gradient). If it gets narrower, depth rises faster (steeper gradient).
Practice questions for Real-Life Graphs
On a distance-time graph, what does a horizontal (flat) section represent?
A distance-time graph shows a section with a negative gradient. Explain what a negative gradient means in the context of a distance-time graph.