Teacher prompt: “Investigate the domino effect using a set of dominoes”
The teacher shows the students the domino effect by lining up a number of dominoes and then lightly pushing the first one, so producing the domino chain reaction. Students have studied mechanics and waves. This is an open-ended investigation where the students must decide on both the dependent and independent variables. Students would satisfy aspect 1 of design (defining the problem and selecting variables) if they:
state a clear research question, for example, “How does the separation between a fixed number of dominoes affect the time it takes for all the dominoes to fall?”
identify the relevant variables correctly, for example, the dependent variable as the pulse speed or time to fall, the independent variable as the separation of the dominoes, and the control variables as the number of dominoes and the surface upon which the dominoes rest.
Under aspect 2 of design (controlling variables) students would earn a “complete” if they addressed the following.
The method of starting the domino motion: for example, a student might use a small inclined plane of fixed length and roll a ball down the incline in order to hit the first domino with the same impulse for the various trials of the experiment.
A method for timing: for example, a student might use two photo-gate timers, one at the start and one at the end of the domino chain, which would be activated by a falling domino. The timer would start when the first domino moves and stop when the last domino moves. They could also just use a stopwatch.
Standardization: students would explain how they would keep the domino chain in a straight line.
Details of controlling the independent variable: there should be discussion as to how the distance between the dominoes is altered and how the distance between consecutive dominoes is made the same for each trial. This would involve stating the two points between which the separation is measured.
A list of materials: this would include a box of dominoes, photo-gate timers or stopwatch, a ramp and small ball for the incline, a metre rule to keep the domino chain at a constant 2.00 m length, and a 30 cm rule for measuring domino separation.
Under aspect 3 of design (developing a method for collection of data) students would earn a “complete” if they addressed the following.
Repeated measurements: students would realize that repeated measurements for the same domino separation are required. An average time would then be calculated.
Scope and limit: students would realize that the minimum separation of the dominoes is when they are touching, face to face, that is, zero separation. Students would also realize that there is a maximum separation that is more or less equal to the height of a domino. Students would ensure that a suitable range of values is chosen between these limits.
Changing the number of dominoes one at a time allows for ample data within the allowed range.
Design:
Example of a design experiment
Teacher prompt: “Investigate the domino effect using a set of dominoes”
The teacher shows the students the domino effect by lining up a number of dominoes and then lightly pushing the first one, so producing the domino chain reaction. Students have studied mechanics and waves. This is an open-ended investigation where the students must decide on both the dependent and independent variables.Students would satisfy aspect 1 of design (defining the problem and selecting variables) if they:
- state a clear research question, for example, “How does the separation between a fixed number of dominoes affect the time it takes for all the dominoes to fall?”
- identify the relevant variables correctly, for example, the dependent variable as the pulse speed or time to fall, the independent variable as the separation of the dominoes, and the control variables as the number of dominoes and the surface upon which the dominoes rest.
Under aspect 2 of design (controlling variables) students would earn a “complete” if they addressed the following.- The method of starting the domino motion: for example, a student might use a small inclined plane of fixed length and roll a ball down the incline in order to hit the first domino with the same impulse for the various trials of the experiment.
- A method for timing: for example, a student might use two photo-gate timers, one at the start and one at the end of the domino chain, which would be activated by a falling domino. The timer would start when the first domino moves and stop when the last domino moves. They could also just use a stopwatch.
- Standardization: students would explain how they would keep the domino chain in a straight line.
- Details of controlling the independent variable: there should be discussion as to how the distance between the dominoes is altered and how the distance between consecutive dominoes is made the same for each trial. This would involve stating the two points between which the separation is measured.
- A list of materials: this would include a box of dominoes, photo-gate timers or stopwatch, a ramp and small ball for the incline, a metre rule to keep the domino chain at a constant 2.00 m length, and a 30 cm rule for measuring domino separation.
Under aspect 3 of design (developing a method for collection of data) students would earn a “complete” if they addressed the following.DATA COLLECTION AND PROCESSING:
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