school physical experiment promoted by digital photographic camera and computer · 2014-11-01 ·...

European International Journal of Science and Technology Vol. 3 No. 8 October, 2014

115

SCHOOL PHYSICAL EXPERIMENT

Promoted by Digital Photographic Camera and Computer

Juraj Slabeycius Department of Chemistry and Physics

Faculty of Education Catholic University in Ružomberok

Nam. A. Hlinku 56,034 01 Ružomberok Slovakia

Daniel Polčin Department of Informatics

Faculty of Education Catholic University in Ružomberok

Nam. A. Hlinku 56,034 01 Ružomberok Slovakia

Corresponding Author’s:

Prof. Juraj Slabeycius, PhD.

E-mail: [email protected] & As.Prof. Daniel Polčin, PhD.

E-mail: [email protected]

European International Journal of Science and Technology ISSN: 2304-9693 www.eijst.org.uk

116

Abstract

Actual paper is focused on the use of new observational and experimental methods in the physical laborato-

ry experiments. This is an example of the utilization of the current digital photography in cooperation with

computers and computer-supported experiments. We point to the possibility of eliminating the need for pho-

tographing objects by illumination with "flashes in the dark" with the classical use of stroboscope.

Modern digital photographic devices allow so called "sequential exposure", which we successfully used for

physical observation of fast moving objects and measurement of e.g. their path, speed and time of movement.

The record of Figures in "sequential exposure" helped us create a sequence of several frames at a single

shutter press in a rapid succession at specified time intervals of fractions of seconds, which are not measur-

able objectively by a stopwatch. Thus we eliminated a relatively large subjective error associated with a

reaction time of a person. Technically well-defined time interval between two positions of the object and

objective determination of its actual position in the made photos are the basis of our observations and phys-

ical measurements of parameters of different types, e.g. mechanical movements.

Physical observations and measurements were also qualitatively and quantitatively analyzed and evaluated

by means of video sequences made by digital photographic equipment. The video sequences were computer-

processed, using programs promoting physical experiment, resp. intended for video analysis of the made

records.

Key words: digital photography, physical phenomena, sequence exposition, video sequence. Foreword

The problem of observation or measurement of physical quantities describing quickly moving objects was in the past solved most frequently with the use of a stroboscope. It is a device to reach a continuous action perception, when the individual and quickly moving phases of action are eye-watched, the mentioned principle is utilised e.g. in cinematography. Stroboscope enables to observe the action in any concrete phase within quick periodical actions as well as to slow them down.

Stroboscope demonstrations are comfortable to excercise by a flashing stroboscope, where the flash-es are produced by a discharge lamp and their frequency may be altered by an electronic device. The flash-ing period is a few microseconds, therefore the observed object appears sharp even at quick motion. If a periodically moving object (rotating etc.) is illuminated by light flashes at the frequency fz of the flashes equal to the frequency fp of the periodical action, the observed action appears to stop. If the flashes frequency is an integral multiple of the observed action frequency, tj. fz = n . fp , the object is illuminated n-times during a period and an observer perceives n different object positions. If the frequency fz does not differ substantially from the frequency fp , the object appears to be in a slow motion and the nature of movement during all the period can be observed.


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Figure 1: A classical stroboscope with an option to set up the flash speed and intensit with

potentiometers. Colour shades: blue, yellow, red, black, white.

Modern flash stroboscopes are digital and utilised in technical environment for an exact measure-ment of revolutions, checking of engines, kog wheel systems, centrifuges, generators and other engine sys-tems.

In the field of medicine, the stroboscope effect of flashing light is employed to ensure to keep e.g.

a 24 hour non-sleep period with a patient. The stroboscope effect is also essential at the discos, where it becomes a part of the perceived rhythm

and overall social ambiance.

Figure 2: Party stroboscope

Figure 3: Scanned periodical movement

European International Journal of Scien

In physics, the stroboscope effecment of objects, to demonstrate the lawobject movement in the homogeneous grdark is illuminated by a stroboscope a permanent shutter or relatively long ex

Figure

Present digital photography provitions. It eliminates the need of the observe.g. „flashes in the dark“, with the classa single laboratory at daylight illuminatiof today relatively widely spread digcurrent analysis of the photo images on Physical observation of moving otime can be carried out by an images ra quick sequence of several Figures 118second. The mode of sequence expositio118enis necessary e.g. to 2 or 3, whereadard etc.) and the memory card capacitytime interva l between 2 Figures, e.g. wto use a stopwatch and also subjective ejectories parts. Recorded images enable measurement of a run trajectory lap. The exactly determined time inteof its current position are essential for types of e.g. mechanical movements. The example of the above-mentiosition at the physics laboratory practiceface. There are several possibilities to de

ence and Technology ISSN: 2304-9693

ect is utilized e.g. to observe a steady and steadilaw of dynamics conservation at objects collisiongravitation field of Earth /free fall, horizontal throe with a given frequency and an image is takexposure period.

re 4: Free fall and horizontal throw

Sequence exposition

vides us with substantially better observation anderved objects photographing and measurement at ssical utilisation of stroboscope. Thus it enables ation of several simultaneous working groups andigital photography devices, there is possible a fon LCD monitors and primarily on computer monig objects and measurement of their e.g. trajectory

record in the mode of „sequence exposition“. 8enis118 press of release, with an exactly set tim

tion - the frequency of Figures (number of Figueas the number of potential Figures depends of thity. The frequency of sequence exposition provi

. with f = 3 s-1 it is 1/3 s. This fixed time interva errors when measuring the times of objects motile an exact location of moving object in a given m

terval between two positions of object and an objr observation and physical measurements of par

tioned application of digital camera with the mode is e.g. the measurement of acceleration of grav

determine g = 9,81 m . s-2.

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dily accelerated move-ions, or to observe the hrow/. An object in the taken by a camera at

nd experimental condi-at the illumination with s independent work in

and with the utilisation following, continuous nitors. ry, speed or movement . The aim is to create

ime of intervals in split

gures in 1 s) can be set the quality (JPG, stan-vides us with an exact val eliminates the need otion on individual tra-n moment and thus the

bjective determination parameters of different

ode of sequence expo-ravity at the Earth sur-

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1. Mathematical pendulum: T = g

lπ2 , where l is a measured pendulum length and T is a pendulum

period determined by e.g. a stopwatch.

g = 2

24

T

lπ

2. Reverse physical pendulum: Tr = g

lrπ2 , where lr is so called reduced length of the physical pen-

dulum, determined experimentally by a series of measurements, and Tr is a corresponding period de-termined graphically by period measurements at different pendulum lengths.

g = 2

24

r

r

T

lπ

3. By the sequence exposition, the acceleration of gravity can be exactly measured from the free fall trajec-

tory, following the relation

s = 2

1gt

2 2

2

t

sg =

where t = 1/3 s is the time interval between the first and the second read position (at the frequency of se-quence exposition e.g. f = 3 s-1 ), and s is the distance of these positions. At this measurement, the use of stopwatch is eliminated and it can also be carried out on a short tra-jectory, which is impossible with a manually operated stopwatch (as in 1 second, an object at the free fall moves along a trajectory of about 5 metres length!).


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Figure 5: Free fall of a table tennis ball


Figure 6: Free fal

With a change of ball weight, the fre

gtv =

Using a digital camera, a well-kn

transformations of mechanical energy foout:

Figure 7: The exp

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fall of a wooden ball

free fall speed independence from the weight of ob

known laboratory practice called „Experimental o forms“ (Physics for the 1st year of grammar sch

xperiment scheme

October, 2014

object can be proved.

l observation of mutual chools) can be carried

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The complicated determination of No.2 ball speed, gained by No.1 ball impact, following the relation

H

gdv

2=

by a measurement of distance d from the diffusion of several impact points of No.2 ball on a surface, is re-placed by a sequence exposition to determine the flown distance s of No.2 ball in the horizontal direction in the above-mentioned time t = 1/3 s, between the first and the second read position

vts = t

sv =

Figure 8: The horizontal throw of a ball

Figure 9: The measurement of ball speed in a horizontal direction

In a similar way the experiments can be simplified and specified by elimination of stopwatch usage at e.g. the laboratory practice called: „Experimental observation of ball movement kinematics on an inclined and horizontal plane“ (Physics for the 1st year of grammar schools):


Figure 10: The experime

Video-sequences

The above-mentioned experimenqualitatively and quantitatively, usinga computer using programs supporting records.

E.g. the program Easy Vid enab

MS Excel. Laboratory set Coach 5 prphysical measurements and observations

Figure 11: Free fall of a ball, pr

Figure 12: The correlation of b

Coach 5 programme

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mental scheme

ents carried out with the sequence exposition cng video sequences made by a digital camerag physical experiment resp. making a video a

ables a simple control and data transmission inprovides a more sophisticated both software and ns.

processed by Coach 5 program

f ball trajectory and elapsed time during a fre

October, 2014

can be analyzed both era and processed in analysis of the ready

into d hardware support to

ree fall, processed by

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Numerous programs enabling toBSPlayer, Viana, provide us with similar

Experiment realization

A ball falls down along a board. with the falling ball is transferred into agrams. By analyses of individual imagemined. These positions are marked on tThen the distances of individual positiotrajectory from the beginning of the fall

Figure 13: Prepar

Subsequently, the students use th

and the elapsed time. The graph shows atime of the fall beginning, the time of thacceleration of gravity g = 9.81 m . s-2 is

Figure 14: A ver

ence and Technology ISSN: 2304-9693

to view individual video sequence Figures, e.g.lar possibilities to analyze the video sequences.

d. Its fall is scanned by a digital camera. The scano a computer. It can be viewed in some of the abges, the ball positions in corresponding time mo the board, along with the time periods from the b

tions from the initial position are measured and tll to the individual marked positions is determined

ared videomeasurement of a free fall

the data to draw a graph of relationship between a steady acceleration of the movement. With the

the last scanned position and its distance from this calculated.

ertical throw processed by Coach 5

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.g. Quick time Player,

canned video sequence above-mentioned pro-

oments can be deter-e beginning of the fall. the length of the ball ed.

en the trajectory length he measured data – the the initial position, the

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Figure 15: An inclined throw processed by Coach 5

Conclusions

It can be said that a digital camera, with an option of the sequence exposition and video sequence,

can be broadly utilised in physical demonstrational and laboratory experiments. It simplifies and specifies the measurements especially when observing rapid processes. It enables independent work of several simul-taneous working groups in a single laboratory and there is a possibility of an instant analysis of the photo images on LCD monitors and on PC monitors.

References

[1] HORVÁTH, P. - ŠEDIVÝ, M.: Analýza mechanického pohybu videomeraním. In: Aktivity vo

vyučovaní fyziky (An analysis of mechanical movement by video-measurement). Bratislava: FMFI UK 2006. (in slovak)

[2] HENNINGES, H.: Nový základný kurz fotografie. Cesta k dokonalej fotografii. (New basic course of photographing. Ways to the perfect photo) Bratislava: Ikar 2002. (in slovak)

[3] KAŠPAR, E. – VACHEK, J.: Pokusy z fyziky na středních školách. (Physical experiments at the high

schools.) Praha: SPN 1967. (in czech) [4] VACHEK, J. a kol. : Physics for the 1st year of grammar schools. Bratislava, SPN 1984. (in slovak) [5] ČERNAK, I.: Tvorba a spracovanie videa. In: Odborný seminár - Využívanie multimédií a

informačných komunikačných systémov vo vyučovaní informatiky, Ružomberok 1. – 2. februára 2007. (in slovak)

school physical experiment promoted by digital photographic camera and computer · 2014-11-01 ·...

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