Question

show work, geo physics

6. a) (3) Explain with sketches why a wagon wheel shown in films can appear to be stationary. What is this effect called? b) (2) How will the wheel appear to be rotating if it then revolves just a little slower? Or just a little faster? c) (2) A wheel has 8 spokes. Through what different angles must the wheel rotate between film frames to appear stationary? Show your work.

Answer 1

as we will learn the wagon wheel effect by taking an example of a clock. Explanation is simple: in films the video is k hown of in frames. After one frome it takes a little time to show another frame ted us take an example when will it look reverse. suppose the hand of the clock is at 12 and the rotation starts after a first frame let's see it comes to q after this frame it comes to 6 then next frame it will come to 3 so on. Real real. in films. In reality it is like shown of in the above figure but in the films it will show like it has rotated from 12 to a to o to 3 and the rotation will look auti clockwise. • This effect is called wagon-wheel effect, or stage coach-wheel effect. so if the rootation rate is such that the hand rotates from 12 to 12 in between the consecutive frames it will appear stationary. I Cam Meanser 360° in a between the frame. . Scanned with

b) If the wheel rotates a bit slower than 360° then it will look in the reverse direction in the film. If it rotates a little bit faster then 360° then it will look in the direction of real rotation, Here We have seen if the rotation is 360° in befassen consecutive frames it will work stationery. le we have 8-spokes they are identical hence if it rotates at an angle 360 = 45° in between the frames it will look stationary. Scanned with CamScanner