Abstract
WITHIN the moderate dimensions of a letter it is hard to give due weight to every aspect of a complicated matter, and while trying to emphasise one side I have somewhat overstated the case, as is evident from the way in which Prof. Lodge has taken me up. I was only considering the teaching of elementary dynamics to engineering students. I do not object to a teacher explaining that inertia is such an important constant property of matter, that equality of inertia is our definition of equal quantities of matter. What I do object to is, a common inversion of this, by which equality of inertia is explained by saying that the quantities of matter are equal. In addition, I urge that teachers of elementary dynamics should call what is usually called mass, inertia, so as constantly to bring before the student the fact that this is the property with which the dynamics of motion deals. I do not plead guilty in this to confusing the issues. The issues of Prof. Perry's review have been overlaid with a discussion as to one of the greatest advances of modern physics, namely the possibility of representing physical quantities by algebraic symbols; but I was trying to recall the original issue, as to the way dynamics should be taught to engineering students. Babes must be treated babyishly, and as long as engineering students are what they are now, and have to attend a variety of lecturers, and read engineering books as they are, I agree with Prof. Perry in recommending that the engineer's unit of inertia be used by their teachers. I have already explained that a multiplicity of units is a very minor difficulty to those who have once grasped what it is that is being measured, but I do think it confuses them, while getting these ideas, for one teacher to use one system, and another system, and for each teacher to call the system of the others by hard names.
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FITZGERALD, G. Dynamical Units. Nature 55, 439 (1897). https://doi.org/10.1038/055439a0
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DOI: https://doi.org/10.1038/055439a0
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