Barometer question

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The barometer question (barometer question ) is a modern legend in education and science . For the solution of a problem that actually has an (institutionally) recognized solution, alternative solutions that are as unconventional as possible are offered. The barometer question is used, among other things, as an anecdote to raise awareness of creativity and lateral thinking.

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There are numerous variants, but they are essentially identical:

"Describe how to determine the height of a high-rise building with the help of a barometer."

The stories and anecdotes around this question are characterized by the fact that a candidate offers a possible solution that deviates from the expected answer, but is theoretically correct. In many versions, the examinee is first accused of having given an incorrect answer, but after protests or questioning impartial parties, the question is then partially or completely answered correctly. It is often said that the exam took place in Copenhagen and that the candidate was the young Niels Bohr . However, there are no reliable sources on this, the oldest known sources are from the 1950s.

Regardless of the discussion about possible authorship, the question and its possible answers have an important didactic side effect: They convey to the learner that one can also achieve the goal with unconventional approaches to a problem that appears clear.

Solutions

The expected answer is that the test object uses the barometer on the floor and on the roof of the high-rise building to determine measured values ​​for the air pressure and uses the barometric height formula to calculate the height of the building (→ barometric height measurement ).

The best known alternatives are:

  • The barometer is connected with a rope and lowered from the roof of the high-rise building. As soon as the barometer touches the ground, the height of the building can be determined by measuring the length of the rope and the barometer.
  • Variation: The barometer is connected with a light rope and lowered from the roof of the building. As soon as the barometer touches the ground, it is pulled up a little and allowed to swing. With the help of the oscillation time, the pendulum length and thus the building height can be calculated.
  • The barometer is dropped from the roof of the building and the duration of the fall is stopped with a stopwatch. The length of the fall and thus the height of the building are determined using the free fall formula .
  • One examines how many “baro-meters” (units of the length of the barometer) the building is high, for example by moving the barometer one by one in the stairwell with the help of markings, and then calculating the “barometer units” into the desired length around.
  • In sunny weather you can set up the barometer and measure the height of the barometer and the length of its shadow. Then the length of the building shadow is determined and the height of the building is calculated from a ratio equation.
  • With a shorter rope, you let the barometer swing as a pendulum first on the ground, then on the roof of the building, and measure the period of oscillation . The different gravitational acceleration is determined from these values and the building height is derived gravimetrically from the difference .
  • The barometer is thrown from the roof into a water container. The height of fall (i.e. the height of the building) can be calculated from the temperature difference using kinetic energy .
  • You throw the barometer from the roof of the building and determine the kinetic energy from the deformation of the barometer.

Complicated:

  • For barometers with brass housing: You throw the barometer from the roof of the building through the pole pieces of a permanent magnet on the floor and determine the Hall voltage at two opposite points on the side of the barometer housing . From this voltage, the speed of the barometer directly before the impact can be calculated, and from this the height of the building can be calculated using the laws of fall .
  • The barometer is accelerated vertically upwards into the air using a seesaw and a weight so that the dead point is at the height of 20 barometer lengths. The weight required for this is now noted. The same thing is done in the next experiment; this time the dead point should be at the height of the roof gable. The “20 barometer height” is multiplied by the factor of the increase in weight required for this, and the result is the “barometer height” of the entire house. This is converted into a desired length dimension. To confirm the altitude, you can measure the actual flight time and use the formula for free fall to calculate the altitude, provided that the acceleration time of the seesaw is also included. In order to be able to prove the whole thing three times, the deformation of the barometer is converted into the height of the building using kinetic energy, since the barometer also falls down.

What is striking about these answers is that the measurements with the barometer ( air pressure ) expected by the examiner are replaced by other measurements ( time , length , temperature or electrical voltage ), so theoretically further aids would be required to determine the building height. If no specific length dimension were given, one could also use the barometer units mentioned above for measuring the rope or the shadow (see above).

There are also other solutions that do not require measurements. These answers are not based on physical or mathematical laws:

  • You visit the caretaker of the building and offer him the barometer in return for telling you the height of the building.
  • The barometer serves as a complaint when looking through the building plans (wherever).
  • You set the building in resonance vibrations by striking it with the barometer until it collapses - the next day the newspaper says how high it was. The barometer can also serve as a paperweight while reading the newspaper.
  • You leave the barometer as a deposit in order to receive a laser differential meter with which you can measure the height of the building. Then the barometer can be triggered again by returning the altimeter.

Web links

See also