Halyard cord

A drop cord is a thread to which pieces of weight are attached at certain intervals. It is held so that the lowest weight touches the ground. If you let go of the thread, you can hear the weight pieces on the floor with a suitable choice of the spacing as an even knocking, in which the time between two consecutive knocking noises is always the same. This shows that with constant acceleration, as is a good approximation here with free fall , the distance covered increases quadratically with time, and on the other hand that the acceleration of the weights is independent of the mass. (Otherwise the acceleration would decrease during the fall, since the masses lying on the ground no longer "pull" the thread.)

In the 16th century, Galileo Galilei investigated the uniformly accelerated movement during free fall with the help of a fall cord .

Calculation of the distances

If the weight pieces are simply attached to the thread at equal intervals s (equidistant), one hears a series of knocking noises that is getting faster. Weight number n hits right now

${\displaystyle t_{n}={\sqrt {\frac {2s_{n}}{g}}}}$ (1)

on.

The following formula is used to calculate the required distances on the thread for identical time intervals t :

${\displaystyle s_{n}={\frac {1}{2}}g(t_{n})^{2}}$ (2)

s (n) is the distance between weight n and weight number 0 , which rests on the floor at the bottom of the thread.

Experimental setup

2 drop cords

Play media file

2 attempts with the fall cords

If, for example, a time interval of 0.18 s is selected, inserting in (2) results in a value of approx. 0.16 m. To determine the position of each additional weight,

${\displaystyle t_{5}=5\cdot 0{,}18~{\rm {s}}}$

multiplied by the ordinal number of the weight. z. B. 5th weight:

${\displaystyle s_{5}={\frac {1}{2}}g(t_{5})^{2}}$

A similar procedure is used for the equidistant line spacing , where s is the distance between the lowest mass and the currently calculated one.

In order to optimally hear the impact of the drop cord, you should work with a sound amplifier, for example with a metal bucket or a sheet metal plate on wood.

The choice of the elevated position and the time of the attempt should also be chosen with care. In windless conditions, the 2nd - 4th is recommended. Floor of a house.

literature

• Helmut Hilscher: University of Augsburg, Institute for Didactics of Physics, CD-ROM Freehand Experiments
• H. Hahn: Physical freehand experiments . Volume 1. Otto Saale publishing house, Braunschweig 1907.
• Dieter Meschede: Gerthsen Physics . Springer DE, January 1, 2010, ISBN 978-3-642-12894-3 , p. 34 (accessed June 1, 2013).

Web links

• Animation of the drop cord ( LEIFI physics)

Individual evidence

1. ↑ Video from Heidelberg University