Speed of falling of a body in air, unlike a vacuum, depends not only on the initial speed, height and acceleration of gravity, but also on air resistance. As influence of the last depends on a shape of a body and hardly gives in to mathematical account, it is the most rational to measure this speed directly.
It is required to you
- - computer with the sound card;
- - two solar batteries from calculators;
- - ruler;
- - construction level;
- - lighting fixture.
Instruction
1. Connect one solar battery from the calculator (large cannot be used) to the left channel of a linear entrance of the sound card, and another - to right. Consider that at some sound cards only an exit, and an entrance - monophonic, and at it is stereophonic, besides, there is a microphone supply voltage. Then connect solar batteries consistently, observing polarity, load with the resistor on 100 kOhm and connect to this entrance via the condenser on 0.1 mkf - it will not pass to them a constant component.
2. Install the Audacity program on the computer. Arrange solar batteries at a surface strictly vertically (using construction level) at such distance from each other that it was about twice less than diameter of the falling body. Direct to them the lighter from distance about a meter. Start the program. In the mode of record make sure that at sharp closing and opening of solar batteries on the oscillogram noticeable indignations appear.
3. Include the record mode in the Audacity program. Dump a body so that it blocked one solar battery in the beginning down, and then - both.
4. Stop record. On the oscillogram (or two oscillograms if the sound card is equipped with a stereophonic entrance), using the scale which is built in the program, measure a period between peaks of indignations. It will be expressed in seconds.
5. Precisely measure by a ruler distance between solar batteries. Transfer it from centimeters to meters. Divide this distance into the period measured by means of the Audacity program, and you receive falling speed just before contact with a surface body. It will be expressed in meters per second. If necessary transfer it to other units, for example, kilometers per hour (1 km/h = 0.2 (7) m/s). Try to compare this speed to calculated by a formula V=sqrt(2hg) where V - speed, by m/s, h - height, m, g - acceleration of gravity, 9.822 m / с2. The less there will be a measured speed in comparison with settlement, the influence of resistance of air is more.