Predict The Velocity Of A Stream

Background: Water in streams flows from areas of high elevation to areas of low elevation. Stream flow is measured by recording the water's velocity. The velocity varies from one stream to another and also in different areas of the same stream. Many components of the stream affect the velocity, including sediment, slope, and rainfall.

Question How does slope affect velocity? Materials

1-m length of vinyl gutter pipe ring stand and clamp water source with hose protractor with plumb bob sink or container to catch water stopwatch grease pencil meterstick paper three-hole punch

Safety Precautions ^EHK^

Procedure 1.

Protractor

String

O-Weight

String

Read and complete the lab safety form. Work in groups of three to four. Use a three-hole punch to make 10 to 15 paper circles to be used as floating markers. Use the illustration as a guide to set up the protractor with the plumb bob.

Use the grease pencil to mark two lines across the inside of the gutter pipe at a distance of 40 cm apart. Use the ring stand and clamp to hold the gutter pipe at an angle of 10°. Place the end of the pipe in a sink or basin to collect the discharged flow of water. Attach a long hose to a water faucet in the sink. Keep the hose in the sink until you are ready to use it. Turn on the water and adjust the flow until the water moves quickly enough to provide a steady flow. Bend the hose to block the water flow until the hose

O-Weight is positioned at least 5 cm above the top line marked on the pipe. Allow the water to flow. Allow the water to flow at the same rate for all slope angles.

10. Drop a floating marker approximately 4 cm above the top line on the pipe into the flowing water.

11. Measure the time it takes for the floating marker to move from the top line to the bottom line. Record the time in your science journal.

12. Repeat Step 9 two more times.

13. Repeat Steps 9 and 10, but change the slope to 20°, 30°, and then 40°.

14. Make a line graph of the average velocity.

Analyze and Conclude

1. Interpret Data What is the relationship between the velocity and the angle of the slope?

2. Apply Describe one reason that a stream's slope might change.

3. Infer Where would you expect to find streams with the highest velocity?

4. Predict Using your graph, predict the velocity for a 35° slope.

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