Geoff I Swan
Department of Applied Science
Edith Cowan University
Perth, Western Australia
Computer assisted experiments using PASCO transducers and software have been introduced into the first year mechanics laboratory at Edith Cowan University. The response of students to these experiments has been overwhelmingly positive. Data from two of the experiments is presented.
Computer assisted experiments were introduced into the new first year unit, "Physics of Motion" in the first semester 1995, at Edith Cowan University. Students were required to use a computer to log data obtained using photogate sensors and then (usually) produce graphs of the observed motion.
PASCO Scientific sensors and software were used in all of the computer assisted experiments [1-3]. Sufficient sensors and PC's - from 286's to 486's - were provided to ensure a group size of between two and three students. Almost all students found the software easy to use even though few students had previously seen or conducted a computer assisted physics experiment. Some of the expected teaching and learning implications of this usage were discussed at OZCUPE2 [4] where early student responses were also presented.
Computer assisted experiments were used in the measurement of:
· the acceleration due to gravity
· the acceleration of a glider on an inclined air track
· the conservation of momentum for two colliding air track gliders
· the coefficient of kinetic friction for a sliding block
· the angular acceleration of rotating platter
Data from the first and last experiments are presented here in order to illustrate how students are using computers in the laboratory.
Students conduct their first computer assisted experiment towards the end of their second laboratory session: measuring the acceleration due to gravity. This is an excellent first computer assisted experiment for the students to do as:
· it is quick and easy
· there is time for several trials
· students are quickly able to master the timing software thus allowing plenty of time for them to concentrate on the physics
Students simply drop a large picket fence through an infrared photogate (Fig 1) connected through a games port (or a Pasco 6500 interface box) to the PC. Once the spacing of 5cm between the pickets is entered, the software is able to calculate the displacement, velocity, and acceleration of the picket fence as a function of time. Students are asked to plot velocity vs time with the statistics and linear regression options on (Fig 2).
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| Fig 1: Picket fence and photogate from [1] | Fig 2: Velocity vs time plot of the picket fence. Slope (in top left hand corner) is 9.810 ms-2. |
The students can instantly read the slope of the graph from the screen and thus the acceleration of the picket fence. They also print the graph which is inserted into their log books as a permanent record.
Results typically vary between 9.70 ms-2 and 9.85 ms-2, which stimulates discussion as almost all students expect to get 9.80 ms-2. They need to critically evaluate their experimental setup and method if they are going to provide a plausible explanation. The variation is in fact due to different amounts of rotational motion given to the picket fence as it is dropped.
In the final computer assisted experiment, students use the Pasco Rotational Apparatus [3] to study both the kinematics and dynamics of rotational motion. In particular, they are asked to measure the moment of inertia of the main platter. The experimental set up (Fig 3) and a typical plot of angular velocity vs time (Fig 4) together with some calculations are shown below:
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| Fig 3: Pasco rotational apparatus from [3]. The smart pulley (where the spokes pass through a photogate) is connected to a PC. |
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| Fig 4: Plot of angular velocity vs time for the platter when acted on by a torque due to a hanging mass of 100g and a moment arm of 2.0cm. The slope gives the angular acceleration. The calculated moment of inertia (I) is comparable to that given by Pasco. |
The motion of the main platter is recorded using a smart pulley (held against the edge of the platter) connected to a PC. The software provides a "rotational apparatus" option so that the PC can calculate the platter's angular displacement, angular velocity, and angular acceleration as a function of time.
For a given torque, students graph the angular velocity vs time for the platter and then read off the constant angular acceleration (Fig 4). The torque on the platter can be varied by changing the hanging mass or the moment arm. The students are asked to determine the angular acceleration for different masses. They can then determine the moment of inertia by plotting the angular acceleration vs hanging mass by hand. The relationship is linear and the slope of this graph is (for a constant moment arm) inversely proportional to the moment of inertia.
Students' attitudes as evidenced by written anonymous survey responses (33 students in 1995) were overwhelmingly positive towards the introduction of computer assisted experiments. 76% of students responded that computers increased their enjoyment of physics and 61% thought that the computers allowed a greater understanding of the physics involved. Based on my observations in the laboratory and my previous experience with similar students I came to the same conclusions; students were speaking more clearly about the physics ideas involved and their learning outcomes were improved.
At the end of the unit, 67% of students believed that the use of computers in the "Physics of Motion" laboratory should be increased or greatly increased with 33% of students believing that the balance was about right. No student thought that there should be less use of computers.
The results of identical surveys in 1996 were similar.
Computer assisted experiments have been successfully introduced into a first year mechanics program. The students enjoyed these experiments which facilitated a greater sophistication in student-demonstrator discussions about the motion under investigation. In any case, the increased student motivation observed in these classes would by itself be expected to encourage students to continue with physics and improve their learning outcomes.
1. Introductory dynamics system with computer timing kit, . 1994, Pasco Scientific.
2. Precision timer program, . 1992, Pasco Scientific.
3. Introductory Rotational Apparatus, . 1994, Pasco Scientific.
4. Swan, G.I. The Introduction of Computers in a Mechanics Laboratory. in Second Australian Conference on Computers in Physics Education. 1995. Melbourne: University of Melbourne.
