1. The British Dam Society
Lesson 1 – Depth and pressure
Forces and dams 11–14 | Lesson 1 – Slide 1

2. What do you know about dams?
What is a dam?
What are they for?
Where are they found?
Forces and dams 11–14 | Lesson 1 – Slide 2

3. What do you know about pressure?
What is pressure?
What causes pressure and how does it change?
What is the formula for pressure?
Forces and dams 11–14 | Lesson 1 – Slide 3

4. Dams today How do we use dams today?
Forces and dams 11–14 | Lesson 1 – Slide 4

5. Prepare your bottle Measure and mark each hole and line.
Carefully make four holes. They must all be the same size.
Label each line and hole.
Fill
Measure
5cm
10cm
15cm
20cm
25cm
Measure from base
Forces and dams 11–14 | Lesson 1 – Slide 5

6. Procedure
Place bottle at least 50cm above the surface on which streams will fall.
Fill to ‘fill’.
Uncover one hole.
Wait until water level reaches ‘measure’.
Observe or measure how far it squirts.
Fill
Measure
5cm
10cm
15cm
20cm
25cm
Measure from base
Forces and dams 11–14 | Lesson 1 – Slide 6

7. What do our results tell us?
Your results should look similar to these.
How does distance change with depth?
What does this tell you about how pressure changes with depth?
Forces and dams 11–14 | Lesson 1 – Slide 7

8. Pressure, depth and dams
Pressure increases with depth because:
The deeper you go, the more water there is above you.
This means there is a greater force pressing down.
If there is more force per unit area, there is greater pressure.
How would you design a dam wall so it can withstand greater pressure near its base?
Forces and dams 11–14 | Lesson 1 – Slide 8

9. The British Dam Society
Lesson 2 – Forces on a dam
Forces and dams 11–14 | Lesson 2 – Slide 1

10. What do you know about forces?
What is a force?
How do forces act?
What can forces make happen?
Forces and dams 11–14 | Lesson 2 – Slide 2

11. What forces act on a dam? Draw the forces acting on the dam.
Forces and dams 11–14 | Lesson 2 – Slide 3

12. What forces act on a dam?
Balanced forces mean the dam is strong and stable.
Unbalanced forces mean the dam will deform or move.
Forces and dams 11–14 | Lesson 2 – Slide 4

13. Build a dam – Scenario 1: farm irrigation
The map shows hilly farmland with streams and a small river.
Where is the best place to store water for when the streams run dry?
Where will the farmer pump the water from?
Where will your reservoir go?
Sketch your dam wall’s cross section.
Forces and dams 11–14 | Lesson 2 – Slide 5

14. Build a dam – Scenario 2: micro hydro
The map shows a valley wall. The hilltop is at the top of the slide and the valley bottom is at the bottom of the slide.
Where is the best place to block the stream, so the water can fall a long way down the pipe to the turbine?
Where will your reservoir go?
Sketch your dam wall’s cross section.
Forces and dams 11–14 | Lesson 2 – Slide 6

15. Build a dam – Scenario 3: drinking water supply
The map shows a valley with streams and a river.
Where is the best place to block the valley to store as much water as possible?
Where will your reservoir go?
Sketch your dam wall’s cross section.
Forces and dams 11–14 | Lesson 2 – Slide 7

16. What forces act on a curved dam?
This is an aerial view of a curved dam that stores water in a steep valley.
The valley sides are strong and made of solid rock.
What happens when the water presses against this curved dam wall?
Forces and dams 11–14 | Lesson 2 – Slide 8

17. What forces act on a curved dam?
The water pressure makes the dam wall want to straighten, pressing it into the valley wall.
The valley wall presses back so the dam does not move.
The water pressure on curved dams helps them stay where they are!
Forces and dams 11–14 | Lesson 2 – Slide 9