Physics | High school » István Bartos-Elekes - Physics classes aided by stroboscopic photographs at the Ady Endre High School

Source: http://www.doksinet M G R EP C PT S BUDAPEST Z ö P ELFT BME C A T V K 1 ö s 2 "1 ~~ e e 1 UPAP i • • ADY • Physics classes aided by stroboscopic photographs at the GIREP-ICPE-EPEC-MPTL 201q CONFERENCE Celebration of Eötvös Year 201q Ady Et1dre 1-ligh School, Oradea - Romat1ia Teachit1g-leart1it1g cot1temporary physics, from research to practice dr. Bartos-Elekes István, ADY Endre Líceum, Nagyvárad l-lu11gary - Budapest - July 1-5, z01q Source: http://www.doksinet Afew words about the albums stroboscopic photographs Toward the end of last century s 70s I had built a calibrated electronic stroboscope, which by the end of the 80s had been augmented with a computer connection based on my freshly issued patent (parallel interface - PIO). The camera f lash controller was operated by a quartz-timer-based TSR program, but the same computer started and stopped the experiment controller and the camera car, handled room lighting, monitored

the camera shutter, and started/ control led/ stopped the experiment, followed by the printing of the experimental data log. Precision light-gates selected the instants of the motion to be photographed. In contrast to the constant-time-interval stroboscopic photography prevalent at the time, I have introduced constant spatial interval photography and custom-interval photography based on a flash-timing interval table. The motion of the car was controlled by another computer (in Master-Slave mode), so the positions and path of the moving object could be illustrated from the point of view of a moving (either at a constant speed or accelerating) observer, illustrating the relativity of motion. An interesting coincidence: in one case, we photograph the free fall of a marble with constant spatial intervals, as observed from an accelerating car. In another measurement we photograph with constant temporal intervals, the marble is in uniform motion, photographed from a uniformly moving car. In

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V> - L +- e . ~ >, > L e O"IO > o L ~ Eo O"I~ +L +- t. V> o v, : : : .- ·- e CL t E +- 0 •- L ~ .o +- > ~ >- E ::> = := ~ e v, O++- -0 ·- +o O O"I ~ +- 0 o ~ ·- t. 0 e +- e t.= e OL e t E ~ ~ + - + E o 0 o +- 0 ·- +- +- ·- +.0 V> V> O 1 - +- e >- +V) e ::J CL 0 0 u t V) ca. ~ ~ L 0 +- t. V) ~ 0 ::J u u V) .0 ~ 0 ~ . ~ O"I e ::J ·0 CL V) u E ~ e O O L -0 ·++. ~ u V> L t. L +- +CL ~ O"I o v, e t. ::J ·O"I O -0 ~ u V) >- ~ +- CL ü .0 0 L ~ ~ - ~ L -- t. +- 0 0 +~ V) > .-, ::J ~ -0 0 L +- ~ +- o e +- +- +0 .:::t: 0 0 0 e 0 E +- -0 t. ~ ::J 0 S +- CL 0 ~ 0t. t V) 0 u CL-~ ~ -0 0 ~ .:::1: 0 e o 0 +0 e ~ -0 +- e 0 +- s ~ t. L +~ L +O"I H e ~ (. u -0 ·>- t. L O ::J s +- O"I ADY Endre Líceum, Nagyvárad Source: http://www.doksinet Fizikum Computer-controlled stroboscope Electronic and co• uter-controlled l!I l!lte• ror

ostrobo=opic photography - con!otruction-de„elop10ent: 1977-2019 Source: http://www.doksinet Af ew words ab out our complex setup ~-~~.- , ~~~ - . - , , .· . •" In 1975 I saw an eight-legged buffalo among the ancient Altamira cave paintings. It immediately inspired me to consider illustrating the trajectories of moving objects to aid in physics teaching. After returning home, I have designed and built an electronic stroboscope. Source: http://www.doksinet gfroboscope cot1trol This classic stroboscope was built in 1977 but by the end of the 80s it was further improved by computer control. The current system consists of an average PC and a rack of home-built electronics. Photography with constant temporal intervals. The flash timing is controlled by a quartz-clock-based TSR (Terminate and Stay Resident) program but the same PC also starts and stops the experiment and the camera car and controls room lighting. Precision Iight gates select the part of the

trajectory to be photographed. Photography with constant spatial intervals (1992). I extended the existing constant temporal interval stroboscope setup with constant spatial interval capability by introducing a flash interval array. With this method, a thousand arbitrary flash intervals can be preset. Source: http://www.doksinet The camera car . . 1 . -·- ~ A robust CNC car with a camera . ~ . 1 , • 1 • . ., • } f astened to it moves on a rai 1 track and provides the observers viewpoint when illustrating the relativity of a trajectory. Optoelectronic position sensor. The cars motion is controlled by a separate computer connected to the f lash-controller PC in Master-Slave mode. Based on about 200 position coordinates, the motion of the car is controlled by the Slave PC according to the predef ined time-motion function. If the flash-timing function is the inverse function of the equation of motion, the stroboscopic photograph shows uniform motion. When external

conditions interfere with the uniform motion, these appear as irregularities on the photograph allowing for the identif ication and measurement of these external factors. Source: http://www.doksinet !• lf• Physies classes aided by stroboscopic photographs at the Ady 1-ligh ~chool •••••• • . i . 1): 1 • • • • • •• • ~ J .!:-;; • ~~ .• f • ~ • 1 • • 1 --- 1 1• ••••••• ••• • • ••• 1 • • • • • • • • • • l ,· j9 •• • • ••• •• •• I ~- • • • • • • •• •• • • • • • • • • • • • L I • • • • • • • • • .• •e / e • • • • • • • . • •• • • • • 1 , • •. e •• .-~) I / / : 1 1. . • • • • • • • • • • • • • • • • • • • • • • My f irst attempts Source:

http://www.doksinet 111 The beginnings . lq77 1 1 l • :í ·1 ., ! . • ·~· !J .,, , ,~+h t ,, · . 11 1•1 1 t \ ,. ~ . ~ • t 1 .,;r• ~ · , ,, ~.::t;: "" . -:.A,tlfiwa, Free fali of a ball Circular motion Simple pendulum Source: http://www.doksinet Projectile motiot1 111 The bouncing of a ping-pong bal!. The ball, arriving from the right, bounces back after losing some energy I did not succeed in capturing the first collision (33 flashes, Dt =50 ms) Source: http://www.doksinet My first pendulum photo. I managed the right cut by taking advantage of the cameras 1 s shutter speed (14 flashes, bit= 80 ms) Source: http://www.doksinet Physics classes aided by stroboscopic photographs at the Ady 1-ligh School•••••. . i . 1): 1 • • ~ J • .&-;;----~~- . •• ••••••• ·•·· •• •• •• • • ••• •• • • • • • • • • • • . •

• • • • • •• •• • • • • • • • • • • • L • l •• ••• 1 I - I • • • • • • • • • • • • • • • • • • • . • •• • 1 , • •• • ! • • • ••• •• . : ~ ~ ·•. • • • • • • • • Classic stroboscopic photographs Source: http://www.doksinet Uniform and accelerating motion (1:4) s = 1,20 m; v = 1,20 m/s; (flt = 100 ms) 11 s= 1,30 m; a= 2,60 m/s 2 ; (flt = 100 ms) Source: http://www.doksinet 11 Uniform and accelerating motion (1:4) . . . 7 . . 0 . S! 0 S! 0 ~ 0 ~ . 0 C<) 0 C<) 0 . . 0 . " " 0 1.1) 0 1.1) . . 0 ,() 0 ,() 0 r-- . . 0 r-- . ~ ~ 0 0- 0 0- 0 . . 0 S! . S! g g 0 • 1 s:! . 0 s:! ] " s = 1,20 m; v = 1,20 m/s; (flt = 100 ms) . 0 !!l ] " s= 1,30 m; a= 2,60 m/s 2 ; (flt = 100 ms) Source:

http://www.doksinet Uniform circular motion , ••••••• •• / An aspirin on the turntable (16 RPM; Ilt = 110 ms) 11 Source: http://www.doksinet Uniform circular motion An aspirin on the turntable (33 RPM; b.t = 110 ms) 11 Source: http://www.doksinet Uniform circular motion An aspirin on the turntable (45 RPM; Ílt = 110 ms) 11 Source: http://www.doksinet 111 Bout1cit1g ping pong ball - tiJ1 • e •• -- The ball, arriving from the right, loses energy after colliding with the table. I did not succeed in capturing the instant of the first collision (47 flashes, Dt =50 ms) Source: http://www.doksinet Real projectile motiot1 Motion of the ping pong bal/ with energy losses after collision with the tabi e (19 f lashes, D.t =60 ms) 11 Source: http://www.doksinet 11 Real projectile motiot1 130 120 110 100 qo - ••• • •• • • go 70 • - 60 50 - 40 30 20 - • 10 0 -- hi(cm] • • ••- -• ht (cm]

l l l l l l l l l l l l l l l l l l l Motion of the ping pong bal/ with energy losses after collision with the tabi e (19 f lashes, D.t =60 ms) 0 10 20 30 40 50 60 70 go qo 100 110 Source: http://www.doksinet 11 Free fali of a milk drop (11 flashes, t-t = 20 ms) Source: http://www.doksinet Physics classes aided by stroboscopic photographs at the Ady 1-ligh School•••••. . i . 1): 1 • 1 • • ~ J .,! ; ~•. •• • • ••• •• •• ••• • • • • • • • • • •• ••••••• ·•·· 1 1 I . •• • •• •••• • • • • • • •• •• • • • • • • • • • • • L - • . • l I • • • • • • • • • • • • • • • • • • • . • •• • 1 , • •• • ! • • • ••• •• . : ~ ~ ·•. •• ••• •• •• ••• The relativity of a

trajectory Source: http://www.doksinet Relativity of a trajeetory 11 This is how an observer at rest sees the trajectory of an object in free fali (photographs at equal time intervals) Source: http://www.doksinet Relativity of a trajeetory 11 This is how an observer moving uniformly to the right sees the trajectory of an object in free fali (photographs at equal time intervals) Source: http://www.doksinet Relativity of a trajeetory This is how an observer at rest sees the trajectory of an object in free fali (photographs at equal spatial intervals) 11 Source: http://www.doksinet Relativity of a trajeetory This is how an observer accelerating to the right sees the trajectory of an object in free fali (photographs at equal time intervals) 11 Source: http://www.doksinet Relativity of a trajeetory 11 This is how an observer accelerating to the right sees the trajectory of an object in free fali (photographs at equal spatial intervals) Source: http://www.doksinet

Relativity of a trajeetory 11 This is how an observer in uniform motion to the right sees the trajectory of an object in uniform descent (photographs at equal time intervals) Source: http://www.doksinet 111 Relativity of a trajectory - - - -- - - ~ 0 - . ~ - , "--~ - 1 -- ~ - - ==-- ~- ~- ~--~ 1 - e- ----------- 1 1 1 1 1: - - ---=--=-=-=--- -~ -- - -------- 1 1 1 1 1 1 1 1 1 1 1 1 I This is how an observer moving to the right with the same uniform speed vas the cart sees the trajectory of a white dot at the perimeter of the cart s wheel Source: http://www.doksinet 111 Relativity of a trajectory 1 1 1•1 :1 r1 i ·,••i ., • 1. i~, " :: !1 i. 1 . :. . . ., ~~----" --- ~ · "" !f~~- This is how an observer at rest sees the trajectory of a white dot at the perimeter of the wheel of a cart that is moving to the right with speed v Source: http://www.doksinet 111 Relativity of a trajectory 1

1 1 1 1 1 1 1 1 1 1 1 1 This is how an observer moving to the right with speed v sees the trajectory of a white dot at the perimeter of the wheel of a cart that is moving to the right with speed 2v Source: http://www.doksinet 111 Relativity of a trajectory - - =-------=-=---=-------------= -- - - - - - ~ - - -- - - - --- - ---==--- - - - ~ -- -~-- - - - - --==------=----------- ~~ =-=-----=- --~ - - - =- JlJ ~~ - - - ~-----~ - -- 1 1 1 1 1 1 1111 111 This is how an observer moving together with an accelerating cart sees the trajectory of a white dot at the perimeter of the cart s wheel Source: http://www.doksinet !• lf• Physics classes aided by stroboscopic photographs at the Ady 1-ligh School•••••. .• . i . 1): 1 • • • ~ J .!:-;; • ~~ ~ • 1 • • 1 --- 1 ••••••• ••• • • ••• 1 • • • • • • • • • • l ,· j9 •• • • ••• ••

•• I ~- • • • • • • •• •• • • • • • • • • • • • L I • • • • • • • • • •• .• I • • • • • • • . • •• • • • • • 1 , • • •• •• .-~) I / / : 1 1. . •••••••••••••••••••••••• Circular motiot1 Source: http://www.doksinet Source: http://www.doksinet Source: http://www.doksinet Source: http://www.doksinet Source: http://www.doksinet !• lf• Physics classes aided by stroboscopic photographs at the Ady 1-ligh School•••••. .• • • • ~ J • ~ • 1 • • 1 1 . •• ••••••• ·•·· •• .:!t--------m;!iiii-~1:11,, •• •• • • ••• •• • • • • • • • • • • . • • • • • • •• •• • • • • • • • • • • • L • l •• ••• 1 I

- I • • • • • • • • • •• • • • • • • . . . • • . • •• • • • • 1 , I • • • • •• •• .-~ I / / : 1 \S 1. •······························· lt1ertia Source: http://www.doksinet 111 When forces of equal magnitude are applied to objects of the same moss, their acceleration will be identical Source: http://www.doksinet lt1ertia of objects ilJ f 1 . ~ I Objects of different masses will move with different accelerations when forces of equal magnitude are applied to them 111 Source: http://www.doksinet Momet1t of it1ertia of rigid bodies 11 Rigid body with large moment of inertia - small angular acceleration (photographs at equal time intervals) Source: http://www.doksinet 11 Momet1t of it1ertia of rigid bodies ~ -- -- -- ~- - ~ ~ -- ~--~ ~ ~ Rigid body with large moment of inertia - small angular acceleration (photographs at equal

spatial intervals) Source: http://www.doksinet Momet1t of it1ertia of rigid bodies 11 Rigid body with small moment of inertia - large angular acceleration (photographs at equal time intervals) Source: http://www.doksinet Momet1t of it1ertia of rigid bodies 11 Rigid body with small moment of inertia - large angular acceleration (photographs at equal spatial intervals) Source: http://www.doksinet !• lf• Physics classes aided by stroboscopic photographs at the Ady 1-ligh School•••••. .• . i . 1): 1 • • ~ • 1 • • 1 -••••••• ,· j9 • • 1 - -.i ~ • ~ J .a ; • •• •• • • ••• •• l •• ••• 1 • • • • • • • • • I • • • • ~- • • •• •• • • • • • • • • • • • L I • • • • • • • • • •• • • • • • • • • • • . • •• • 1 , •• • ! • •

• ••• •• . : ~ ~ ·•. • • • • • • • • • • • • • • • • • • • • • • • Elastic collisioHs Source: http://www.doksinet The left pendulums ball centrally collides with the other pendulum at rest and stops. The other pendulum moves on with a small loss of momentum (12 flashes; D.t =481 ms + 10x60 ms) Source: http://www.doksinet The left pendulums bal! centrally collides with the other pendulum at rest and stops. The other pendulum moves on with a small loss of momentum (11 flashes; tit= 60 ms) Source: http://www.doksinet 111 Elastic collisioH --.------,---~,-~-----+-----+------- . qo ---,---,---,---,---,--so go o-. 0 10 20 30 40 60 10 100 110 The ivory bal! on the left collides non-centrally with the other bal! at rest. I did not succeed in capturing the exact moment of collision (12 flashes; D.t = 75 ms) 120 130 140 Source: http://www.doksinet 111 Elastic collisioH • • • • ir ; f. ~,

~I ,,,• • n . • I[ , J [ 1 1 1 1 1 The steel ball on the left collides non-centrally with the other ball at rest. Only the top part of the bal Is reflects light back into the camera (tit= 100 ms) Source: http://www.doksinet Elastic collisioH 111 The pingpong ball is detected by the light gate sensor, then it bounces back from the slanted steel plate (8 flashes; ~t = 50 ms) Source: http://www.doksinet Elastic collisiot1 11 The pingpong ball is detected by the light gate sensor, then it bounces back from the slanted steel plate (8 flashes; b.t =50 ms) Source: http://www.doksinet !• lf• Physics classes aided by stroboscopic photographs at the Ady 1-ligh School•••••. .• . i . 1): 1 • • • ~ J .!:-;; • ~~ ~ • 1 • • 1 --- 1 ••••••• ••• • • ••• 1 • • • • • • • • • • l ,· j9 •• • • ••• •• •• I ~- • • • • • •

•• •• • • • • • • • • • • • L I • • • • • • • • • •• • • • • • • • • • • . • •• • 1 , •• • ! • • • ••• •• . : ~ ~ ·•. • • • • • • • • • • • • • • • • • • • • • • Motiot1 ot1 a slope Source: http://www.doksinet 111 Motiot1 ot1 a slope The first flash fires at the moment the current on the electromagnet (EM) is disconnected, however, the car is delayed by the remanence of the EM (11 flashes; D.t =100 ms) Source: http://www.doksinet Motiot1 ot1 a slope When the current on the electromagnet (EM) is interrupted and the first flash is f ired, the slab could immediately start sliding but is delayed by the remanence of the EM (5 flashes; !::.t =250 ms) 111 Source: http://www.doksinet Motiot1 ot1 a slope The arrows above the measuring stick indicate the expected positions in the absence of the

electromagnet s puli When the current on the electromagnet (EM) is interrupted and the first flash is f ired, the slab could immediately start sliding but is delayed by the remanence of the EM (5 flashes; D.t =250 ms) 111 Source: http://www.doksinet 111 Motiot1 ot1 a slope Looping motion of a ping pong ball (21 flashes; ~t = 50 ms) Source: http://www.doksinet !• lf• Physics classes aided by stroboscopic photographs at the Ady 1-ligh School•••••. .• . i . 1): 1 • • • ~ J .,~~ • .! ; ~ • 1 • • 1 -••••••• ,· j9 • • 1 - ••• • •• • • ••• •• l •• ••• 1 • • • • • • • • • I • • • • ~- • • •• •• • • • • • • • • • • • L I • • • • • • • • • •• • • • • • • • • • • . • •• • 1 , •• • ! • • • ••• •• . : ~ ~

·•. ••••• Circular motion - Oscillatory motion Source: http://www.doksinet Cot1t1ectiot1 betweet1 circular at1d oscillatory motiot1 Circular motion of a ball as seen from the axial direction of the rotation Source: http://www.doksinet Cot1t1ectiot1 betweet1 circular at1d oscillatory motiot1 When observed from the plane of the circle, circular motion appears similar to oscillatory motion Source: http://www.doksinet Connection between circular and oscillatory motion The motion of the elastic pendulum resembles the projection of circular motion 11 Source: http://www.doksinet Cot1t1ectiot1 betweet1 circular at1d oscillatory motiot1 When circular motion (a) is observed from the plane of the motion (b) it appears like an oscillatory motion (e) 111 Source: http://www.doksinet !• lf• Physics classes aided by stroboscopic photographs at the Ady 1-ligh School•••••. .• . i . 1): 1 • • ~ • 1 • • 1 -••••••• ,· j9

• • 1 - -.i ~ • ~ J .a ; • •• •• • • ••• •• l •• ••• 1 • • • • • • • • • I • • • • ~- • • •• •• • • • • • • • • • • • L I • • • • • • • • • •• • • • • • • • • • • . • •• • 1 , •• • ! • • • ••• •• . : ~ ~ ·•. • • • • • • • • • • • • • • • • • Mechanical oscillations Source: http://www.doksinet Oscillations Classic stroboscopic photograph. It is impossible to guess the complete half-period without a CNC stroboscope! 111 Source: http://www.doksinet 111 Oscillations Determining the f irst quarter of the simple pendulum s period (2 flashes; bit = 616 ms) Source: http://www.doksinet 111 Oscillations Determining the simple pendulum s first half-period (21 flashes; !:::.t = 616 ms) Source: http://www.doksinet

Oscillatiot1s The period is reduced after shortening the effective length of the pendulum and therefore we need to employ shorter time intervals for photographing (15 flashes) 11 Source: http://www.doksinet Oseillatiot1s First half-period of the elastic pendulum. Classic stroboscopic photography (15 f lashes; L:t = 100 ms) Source: http://www.doksinet Oseillatiot1s 40 ------. 4 • 20 ------. -20 ------. -40 ~ t -60 First half-period of the elastic pendulum. Classic stroboscopic photography (15 f lashes; L:t = 100 ms) Source: http://www.doksinet ~imple, pet1dulum at1d sprit1g pet1dulum -- - - - The trajectory of simple p~um- - 11 Source: http://www.doksinet 111 Oscillations 1 I I . I , . . ·•···· · ; . 1 , - Part of the first half-period of the oscillations of a bob suspended on a steel wire (11 flashes; ~t = 100 ms) Source: http://www.doksinet Oscillatiot1s First half-period of the oscillations of , bob suspended on a steel wire (21

f/ashes; M =71.6 ms) 11 Source: http://www.doksinet Physics classes aided by stroboscopic photographs at the Ady 1-ligh School•••••. . i • • •• . 1): 1 • • • ~ J • .& ;; ~:. • • f • • • 1• ••• • •• • • ••• •• • • • • • • • • • •• ••••••• ·•·· • • • • • • • •• •• • • • • • • • • • • • L • . l •• ••• • 1 I . - I • • • • • • • • • • • • • • • • • • • • . • •• • 1 , •• ! • •• .· 0. i,D • • •• • • ••• •• • :• . : ~ ~ ·•. • • • • Damped oscillatiot1s of the elastic pet1dulum Source: http://www.doksinet Damped oscillations of an elastic pendulum Weak friction. The small piece of chalk is tied to the oscillating bobs string (250 flashes; At = 60

ms) 111 Source: http://www.doksinet Damped oscillations of an elastic pendulum ••• • •• •• • •••· • • . • •• • • •• •e • • • , Stronger friction. The piece of chalk is tied to the oscillating bobs string (250 flashes; At = 60 ms) 111 Source: http://www.doksinet Damped oscillations of an elastic pendulum 1 •• • e ~ • t, •• ••• •• •f Strong friction. The piece of chalk is tied to the oscillating bobs string (250 flashes; At = 60 ms) 111 Source: http://www.doksinet Physics classes aided by stroboscopic photographs at the Ady 1-ligh School•••••. . i • • •• . 1): 1 • • • ~ J • .& ;; ~:. • • f • • • 1• ••• • •• • • ••• •• • • • • • • • • • •• ••••••• ·•·· • . • • • • • • •• •• • • • • • • • • • • • L •

l •• ••• • 1 I . - I • • • • • • • • • • • • • • • • • • • . • •• • 1 , • •• • ! • • • ••• •• . : ~ ~ ·•. • • • • • • • • Compout1dit1g orthogot1al oscillatiot1s Source: http://www.doksinet Compout1dit1g orthogot1al oscillatiot1s .• ., JI , ,. Equilibrium position of the ball suspended on the long spring , a Source: http://www.doksinet 111 Compout1dit1g orthogot1al oscillatiot1s First quarter of the period of a ball undergoing compound oscillations Source: http://www.doksinet Compout1dit1g orthogot1al oscillatiot1s • • 4t •. 0 •• ·• • Source: http://www.doksinet 111 Compout1dit1g orthogot1al oscillatiot1s . •• • • • • , Motion of a ball undergoing compound oscillations. Emergence of the Lissajous pattern Source: http://www.doksinet 111 Compout1dit1g orthogot1al

oscillatiot1s . . . ! - • .• ;- ; : : : Motion of a ball undergoing compound oscillations Part of the Lissajous pattern has formed Source: http://www.doksinet !• lf• Physics classes aided by stroboscopic photographs at the Ady 1-ligh School•••••. .• . i . 1): 1 • • • ~ J .!:-;; • ~~ ~ • 1 • • 1 --- 1 ••••••• ••• • • ••• 1 • • • • • • • • • • l ,· j9 •• • • ••• •• •• I ~- • • • • • • •• •• • • • • • • • • • • • L I • • • • • • • • • •• .• I • • • • • • • . • •• • • • • • 1 , • • •• •• .-~) I / / : 1 1. . • • • • • • • • • • • • • • • • • • • • • • • • • gurface waves Source: http://www.doksinet Surface waves Circular waves on

the surface of mercury (24 flashes; .6t = 44 ms) 11 Source: http://www.doksinet 111 ~urface waves - . - - - - - ~ - = = = ~~ -- Plane waves on the surface of mercury (.6t = 60 ms) -· Source: http://www.doksinet 111 Diffraction of plane waves after passing through a narrow slit (~t = 44 ms) Source: http://www.doksinet Surface waves Youngs experiment (24 flashes; ~t = 44 ms) 11 Source: http://www.doksinet Physics classes aided by stroboscopic photographs at the Ady 1-ligh School•••••. . i . 1): 1 • 1 • • ~ J .,! ; ~•. •• • • ••• •• •• ••• • • • • • • • • • •• ••••••• ·•·· 1 1 I . •• • •• •••• • • • • • • •• •• • • • • • • • • • • • L - • . • l I • • • • • • • • • • • • • • • • • • • . • •• • 1 , •

•• • ! • • • ••• •• . : ~ ~ ·•. • • • • • • • • • • • • • • • ~tat1dit1g waves it1 strit1gs Source: http://www.doksinet ~tat1dit1g waves it1 strit1gs By adjusting the string s tension and the frequency of excitation, we obtain a standing wave with a single antinode 111 Source: http://www.doksinet ~tat1dit1g waves it1 strit1gs By adjusting the strings tension and the frequency of excitation, we obtain a standing wave with two antinodes 111 Source: http://www.doksinet ~tat1dit1g waves it1 strit1gs By adjusting the strings tension and the frequency of excitation, we obtain a standing wave with three antinodes 111 Source: http://www.doksinet ~tat1dit1g waves it1 strit1gs By adjusting the strings tension and the frequency of excitation, we obtain a standing wave with four antinodes 111 Source: http://www.doksinet ~tat1dit1g waves it1 strit1gs By adjusting the string s tension and the frequency of

excitation, we obtain a standing wave with five antinodes 111 Source: http://www.doksinet ~tat1dit1g waves it1 strit1gs By varying the strings tension and the frequency of excitation, we can change the number of antinodes 111 Source: http://www.doksinet ~tat1dit1g waves it1 strit1gs 111 Refraction of standing waves. Left of the node the string is made of three threads, while on the right it is made of a single thread, therefore, the wavelength is shorter Source: http://www.doksinet Physics classes aided by stroboscopic photographs at the Ady 1-ligh School•••••. . i . 1): 1 • 1 • • ~ J .,! ; ~•. •• • • ••• •• •• ••• • • • • • • • • • •• ••••••• ·•·· 1 1 I . •• • •• •••• • • • • • • •• •• • • • • • • • • • • • L - • . • l I • • • • • • • • • • • •

• • • • • • • . • •• • 1 , • •• • ! • • • ••• •• . : ~ ~ ·•. • • • • • • • • • • Photos oH miscellaneous topics Source: http://www.doksinet 11 Arehimedes serew d 2 ;, ( i. l 1 1 1 1 d 4 1 1 1 1 1 : ! 1 1 1 1 1 1 , 1 ~ • .1 m=50g W M=lOOg 1 1 l ~ m=50g 1 .r 1 ,, / ,, i ( j M=lOOg 1 1 (, m=50g ~ M=200g 1 1 1 m=50g " 1 Under a constant active force, if the number of pulleys is increased, their load can be increased as well, but the distance traveled decreases proportionally. Therefore, one can save on the force applied, but the work performed does not change ~ { ,, ( , 1 1 ,,., ( Source: http://www.doksinet 111 Let1zs law When the ring approaches the electromagnet, the current induced in it slows it down. The ring is about to stop Source: http://www.doksinet Accelerating motion - 1q77 111 An athlete at the start line. Photograph

taken in complete darkness on the track (n = 3 flashes; ~t = 150 ms) Source: http://www.doksinet Uniform motion - 1q77 Near-uniform motion. Stroboscopic photograph taken in complete darkness on the track (n = 3 flashes; ~t =150 ms) Source: http://www.doksinet Data analysis - 1q77 , , ·! , 1 . , , I 1, I I I - 1 - .- • • •• • •• •• • On the day the photos were token I have recorded the distances and time intervals between flashes. Later I have com ared them with those on the hotogra hs Source: http://www.doksinet Dont let the physics teacher near the playgrout1d! Source: http://www.doksinet The large majority of these stroboscopic photographs were token at the "Fizikum" physics laboratory of the Ady Endre High School in Nagyvárad beistvan@yahoo.com