Session 4: Measuring the drag of different forms, different degrees of roughness and at different wind speed

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Objectives: In this experiment the students will measure the drag using a dynamometer.

 Explanation:

Measuring the drag this way, changhing the variabiles on by one, gives them a better understanding of drag and what are the variabiles that influence drag and what can be done to reduce drag.

Material:

different forms: few flat plates, cubes, an aerodynamic form very polished, emery
paper with different degrees of roughness

an aeromodel

a dynamometer

a fan

Maximum duration:

1 hour

Main questions to be asked:

After doing all the previous experiments and the next experiment ask them to tell you what influences drag and why.

Introduction/Starters

Remind your students of session 1. Ask them to tell you which form, they think produces less drag. Ask them to keep that in mind when they will do the following measurements.

Main activities

Ask the pupils to take a cube and put it on the table and to chain it with a rope like in this picture and then ask them to hang the dynamometer from the end of the rope. Place the fan in front of the dynamometer and start it. Ask them to write the indication of the dynamometer in a chart like the one below. Repeat the experiment at least five times and then mediate.

Object	Smooth Cube	Cube having asmall degree of roughness	Cube having a bigger degree of roughness
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Mediate

 Repeat the experiment using cubes with different degrees of roughness that they used at the previous experiment. Ask them to write down the indication of the dynamometer in the same chart. What is the conclusion?

Repeat the same experiment but instead of the cube use o ball. Ask them to make another chart and on the
first line to write the result for the first cube and in the second line to write the result for the ball.

Repeat the experiment once again this time using an aeromodel. Ask them to write the result on the third line of the chart. What is their conclusion?

Object	Smooth Cube	Ball	Aeromodel
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Mediate

Repeat the same experiment using the aeromodel, but this time increase the speed of the wind. Put both results in the same chart. What is your observation?

Aeromodel	Low Speed	Medium Speed	Hight Speed
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Mediate

Conclusion / Plenary

Measuring the drag this way, changing the variables on by one, gives them a better understanding of drag and what are the variables that influence drag.

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