August 30, 1943
Mr. H. H. Windsor, Jr.
Editor, Popular Mechanics Magazine
200 East Ontario Street
Chicago, Illinois
Dear Sir:
I happened to see a copy of the July issue of Popular Mechanics Magazine, and to read an article entitled "Uncle Sam Picks an All-Star Team" by Wayne Whittaker, in which there is reproduced a test, labeled "Copyright, The Psychological Corporation", which is said to be similar to tests used by the Amy. On pages 52, 53, and 54 of the Magazine there are given twelve questions with accompanying drawings, with the answers given on page 146. I am shocked by the fact that three of the twelve answers are wrong, and I am writing to find out if there is any excuse for this. In particular, I hope that you can assure me that this particular test is not used by the Army— I hope very much that the able young men taking Army tests are not handicapped by having their examiners so lacking in ability as to assign incorrect answers to twenty-five per cent of the questions.
The three questions for which incorrect answers are given are Numbers 3, 4, and 6.
No. 3 shows a drawing of a glass of water with chunks of ice floating at the top of the water. The question asks at which point is the water colder, with reference to a point A about an inch below the ice and a point B at the bottom of the glass. The answer is given as A. However, if the water is above 4º C, convection currents will cause the cold water immediately about the ice to flow to the bottom of the glass, which will fill with cold water at 4º C from the bottom up; hence under these conditions point B will be colder than point A. When the water throughout the lower part of the glass reaches the temperature 4° C the two points will be at the same temperature, and only at overall temperatures less than 4° C will point A be colder than point B.
The fourth question relates to a drawing of a uniformly filled freight car on a slanting track, and pushing against the bumper; the question asks which wheel presses down harder on the rail, and the answer is given as A, which is the wheel nearer the bumper. However, it is easily shown by resolution of the force of gravity acting on the center of mass of the freight car into two components, one parallel to and one perpendicular to the rail, that both pairs of wheels press down equally hard on the rail. Hence the wrong answer is given to this question.
The sixth question shows two balloons, one round and one elongated, and asks if the balloons weigh the same and contain the same volume of gas, which one will float higher in the air. The answer is given as A, the elongated balloon. The correct answer is that the two balloons, which weigh the same and contain the same volume of gas, would float equally high in the air. If the question were phrased to ask which balloon would rise the more rapidly, the answer would be balloon B, since an elongated balloon mowing in a direction perpendicular to the direction of elongation would show more frictional resistance than a round balloon. Hence no matter which interpretation is given to the question, the answer as given is wrong.
I shall be pleased to have you tell me why such a simple set of questions should have twenty-five per cent of the answers incorrectly given.
I should like to keep a copy of this issue of the magazine for reference. Will you please have the Circulation Department send me a copy of the July 1943 issue, and I shall send the money for it.
Very truly yours,
Linus Pauling
LP:jr
August
30, 1943
