October 27, 2016

Fizyka: Ruch niejednostajny i prostoliniowy jednostajnie przyspieszony

Ruch, podczas którego prędkość ciała zmienia swoją wartość w miarę upływu czasu, nazywa się ruchem niejednostajnym. Dla tego ruchu charakterystyczne są:
  • Prędkość chwilowa Vch
    Vch = Δx/Δt
    gdzie:
    Δx - przemieszczenie
    Δt - mały przyrost czasu
  • Prędkość średnia Vśr
    Vśr = sc/t
    gdzie:
    Vśr - prędkość średnia
    sc - całkowita droga
    t - czas
Prędkość chwilowa - prędkość ciała w danej chwili; określa się ją jako iloraz przemieszczenia do bardzo małego przyrostu czasu, w którym ono nastąpiło.

Ruch niejednostajny - ruch, w którym wartość prędkości zmienia się w czasie.

Prędkość średnia - iloraz całkowitej drogi i czasu trwania ruchu.

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Przyspieszeniem nazywa się iloraz przyrostu prędkości i czasu, w którym ten przyrost nastąpił.

Wartość przyspieszenia a

a = Δv/Δt

Kierunek i zwrot przyspieszenia w ruchu jednostajnie przyspieszonym prostoliniowym są takie jak kierunek i zwrot prędkości.

Jednostką przyspieszenia w Układzie SI jest 1 m/s², gdyż [a] = m/s².

W ruchu jednostajnie przyspieszonym prostoliniowym przyspieszenie ma wartość stałą.

Image result for ruch jednostajnie przyspieszonyW ruchu jednostajnie przyspieszonym droga jest wprost proporcjonalna do kwadratu czasu, prędkość rośnie wprost proporcjonalnie do czasu, a przyspieszenie ma wartość stałą.
Przyspieszenie jest wielkością wektorową.

Ruch prostoliniowy jednostajnie przyspieszony - ruchu, w którym tor jest linią prostą, odcinki drogi pokonywane w kolejnych sekundach mają się do siebie tak, jak kolejne liczby nieparzyste, a droga jest wprost proporcjonalna do kwadratu czasu.

W ruchu jednostajnie przyspieszonym prostoliniowym droga rośnie wprost proporcjonalnie do kwadratu czasu.

s = at²/2 
gdzie:
t - czas trwania ruchu
s - przebyta droga
a - przyspieszenie  

October 19, 2016

Zdzisław Beksiński (Ostatnia Rodzina)

Zdzislaw Beksinski in Sanok-crop.jpg
Yesterday my Mom dragged me to see a movie about a Polish painter, Zdzisław Beksiński. I didn't really like the movie, because I didn't understand it. I've never even heard of this painter before, and I've never seen any of his paintings.

The movie starts when Beksiński's son, Tomasz, moves to Warsaw in early 1970s. Tomasz is a young, single guy who has psychological problems. Throughout the movie he tries to commit suicide a few times. And at last, at the end of 1999  he succeeds. 

Zbigniew Beksiński lived in a typical communist apartment block on the outskirts of Warsaw (very close to my Mom's old house). He worked from his apartment creating tens of paintings every year. At that time people did not understand his art. It was too dark and weird.

Beksińki shared his apartment with his wife, mother and mother-in-law. His son lived in the apartment block nearby. They lived a simple and difficult life in the communist Poland. Beksiński's wife, Zofia, was portrayed in the movie as a loving and caring wife, mother and daughter-in-law. She was the one who took care of everything and everyone. 

Beside painting Beksiński was interested in filming and photography and at the end of his life in computer graphics.

He was brutally murdered by a 19 years old son of his acquaintance. He was the last one in his family to die.

Here is a short film about Beksińki's everyday life. Most of it was filmed by the painter himself.
There are many films about him on YouTube as he loved documenting his family on film. After his death many of those films were made public.


And here are some of his paintings. Personally I don't really like them.





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Zdzisław Beksiński
24 February 1929 - 21 February 2005

October 1, 2016

Physics: Bernoulli's Principle

Pressure
  • Pressure is the force per unit area on a surface.
  • Fluid pressure results from the motion of the atoms or molecules that make up the fluid.
  • Pressure at a given level in a fluid is the same in all directions. Pressure decreases with altitude and increases with depth.
Transmitting Pressure in a Fluid
  • According to Pascal's principle, an increase in pressure on a confined fluid is transmitted equally to all parts of the fluid.
  • A hydraulic device works by transmitting an increase in pressure from one part of a confined fluid to the other. A small force exerted over a small area at one place results in a large force exerted by a larger area at another place.

Image result for forces in fluids

Floating and Sinking
  • The upward force on a object submerged in a fluid is called the buoyant force.
  • The buoyant force on an object is equal to the weight of the fluid displaced by the object. This is Archimedes' principle.
  • An object will sink, rise to the surface, or stay where it is a fluid depending on whether its density is less then, greater than, or equal to the density of the fluid.
Applying Bernoulli's Principle
  • The pressure in a fluid decreases as the speed of the fluid increases. This is Bernoulli's principle.