A model is held stationary in a low-speed classroom airflow. The horizontal support force balances the opposing drag when the model is steady. Available equipment and procedure options: Use a guarded variable-speed fan, air-speed meter, low-range force sensor and adjustable model mount; subtract the support-only force measured in the same airflow. Design an investigation of how the measured air speed at the model affects the horizontal force needed to hold the model still. Include a reasoned hypothesis, an appropriate range, controls, repeat measurements, a results table or graph, and one specific limitation and safety measure. Do not invent experimental results.

Question

Accepted Answer

Vary the measured air speed at the model; measure the horizontal force needed to hold the model still. Predict Drag should rise with air speed, potentially more rapidly than a straight-line relationship. Keep model shape, orientation and position constant, repeat each setting, and use the evidence to test the prediction. State a testable research question linking the measured air speed at the model to the horizontal force needed to hold the model still, rather than asking vaguely which arrangement is best. A suitable prediction is: Drag should rise with air speed, potentially more rapidly than a straight-line relationship. Justify that prediction scientifically: Faster flow delivers more moving air and a larger momentum change each second. This is a hypothesis to test, not a result that the experiment must produce. Use 1, 2, 3, 4 and 5 m/s as the planned independent-variable settings. Measure the response using the supplied equipment: Use a guarded variable-speed fan, air-speed meter, low-range force sensor and adjustable model mount; subtract the support-only force measured in the same airflow. Record quantities with units before calculating any derived result. Keep model shape, orientation and position constant. This isolates the proposed cause; changing these conditions at the same time would allow competing explanations for any difference. Take at least three independent trials at each setting, resetting the apparatus each time. Tabulate the setting, individual responses and mean; plot the mean response against the changed quantity and show the range of repeated values. Evaluate this specific limitation: Fan setting is not air speed; measure speed at the actual model location. More repeats alone do not necessarily correct a biased method. Protect participants and equipment by this precaution: Keep fingers, hair and loose materials away from the guarded fan; switch it off before changing models.

How quickly does drag grow?

What a complete response should do

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