The dependent variable is the angle the hanging board deflects from the vertical with different wind speeds. It is important that this also be measured accurately, and this can be achieved by attaching a protractor in front of the board, and recording the angle the board deflects with each wind speed.
There are a number of factors that need to be considered in detail to ensure that accurate and reliable results are obtained from this experiment. Primarily, the way wind is produced by the fan needs to be observed. The fan blades cut through the air as it rotates, and due to this the wind speed varies slightly. On using the fan facing the hanging board, this would cause the board to flicker, practically making the angle of deflection difficult to measure. However, this problem can be overcome by facing the back of the fan towards the board. The suction of air through the back of the fan can imitate the smoothness of natural wind, and doing so, the board should stay at the angle of deflection, which can then easily be measured.
Another observation that can be made is that on sucking air through the fan blades air is drawn in from all possible directions.
As the experiment is to observe horizontally moving air, the experiment must be conducted in a confined space, and for this experiment this will be achieved by placing all apparatus within a box.
The board needs to be hanging freely, and this can be achieved by attaching the board to a clamp and stand with sellotape.
Diagram:
Method
1. Set up the apparatus as shown in the diagram. Ensure that the protractor is attached so that the board hangs at 90°.
2. Set the fan to its first wind speed, and record the wind speed displayed on the digital anemometer.
3. Wait for the hanging board to take a deflected position, and measure this angle of deflection from the vertical.
4. Repeat steps 2 and 3 with all other fan speed settings.
5. Repeat step 2 – 4 twice so that overall three sets of results are obtained.
References:
