This example from the PEEL CD-ROM illustrates
Teaching for Quality Learning Principle 12:
Promote assessment as part of the learning process

Find the Formula

Greg Lancaster, Eumemmerring Secondary College

My Year 12 Physics class were revising their work in readiness for the forthcoming test Common Assessment Task in November.

It was becoming apparent that many of the students were experiencing considerable difficulty with interpreting the questions, selecting the relevant formula and correctly identifying the right numbers to use from the garbage of misinformation so often skillfully supplied in many test questions for the purpose of confusion.

I was keen to design a task which would help these students to focus on practicing and hopefully improving these skills, without involving the diversion of number crunching. Often I have seen students get quickly bogged down in the tedious manipulation of formula and numbers without paying enough attention to considering the purpose of their pursuit. The crunching of numbers to quickly arrive at a result becomes an end itself. Little time is spent on interpreting the question, and on checking to see if their result actually answers the question.

The task I developed involves a series of questions with no numbers at all. It originally focused on just identifying the correct formula to use, but was made more difficult by the absence of one necessary quantity and the inclusion of one distracting piece of information as well.

Students were asked firstly to identify the correct formula they would use to solve the problem. They then needed to identify the quantity which was missing and lastly they were asked to identify the quantity which was included as the distracter.

The questions I composed are quite subject specific and I have included several I used for those who may be familiar with the VCE physics course. However I will try to illustrate the task with an easier example more familiar to most.

Example: Speed = distance/time

A similar question in the above style to focus on this formula may read:

Q: You are asked to calculate the distance a car has travelled during its journey. You are provided with the average speed of the car and its mass.

Clearly the quantity missing is the time taken for the journey and the distracter is the mass of the car.

Several of the questions and the instructions I used with the students are listed below.

YEAR 12 PHYSICS - FIND the FORMULA

1. In each of the following situations you are asked to select the correct formula or formulae from your sheet and to identify the item of information which is missing that prevents you from solving the problem. There is also at least one item of information to identify which is not important to the problem's solutions.
2. A car is traveling around a selection of circular road way. You are asked to calculate the magnitude of the frictional force of the tyres on the road. You are given the mass of the car, its speed and instantaneous direction.
3. A photon of light is incident on a metal surface. You are given Plank's Constant, the velocity of light and the work function of the metal. The problem is to calculate the energy of the incident photon.
4. A car collides with a stationary truck of known mass. Both couple together and continue on in the same direction. Given that the velocity of the approaching car and the initial momentum of the truck is provided, find the final velocity of the coupled vehicles.
5. A straight metal rod with a circular cross-section is deformed by a compressive force of stated value. The amount of compression is measured and also stated. You are provided with the density of the rod, Young's Modulus for the metal and asked to calculate the length of the rod.
6. A satellite is in a circular orbit around a much more massive planet. You are asked to calculate the satellite's period of orbit. The question provides you with the mass of the satellite, the gravitational constant {G} and the radius of the satellite's orbit.
7. A suspended spring of a stated mass per unit length is stretched by an applied force. The question provides the magnitude of an applied force and the final length of the spring after extension. A second known force is then applied and the final length of the spring is given. You are then asked to calculate the total energy stored in the spring when the second force is applied.

How did it go?

The students spent about 30 minutes attempting 10 questions.  We spent some time reviewing the answers and about 20 minutes discussing the benefits of the task.  Most felt it was a valuable experience as it made them focus on reading and understanding the question without involving any mathematical task.  They all agreed as I do that one distracter was quite enough.  Any more may only create real confusion.  I feel the exercise was successful and I will use it again maybe with aYear 11 class during a topic revision.

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