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Thread: Which of the following describes fluid pressure against a flat surface?

  1. #1 Which of the following describes fluid pressure against a flat surface? 
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    20. Which of the following describes fluid pressure against a flat surface?

    (A) The pressure is equal to the change of momentum of the fluid molecules as they collide with the surface of the object divided by the time and the surface area.
    (B) The pressure is equal to the change in kinetic energy of the fluid molecules as they collide with the surface of the object divided by the time and the surface area.
    (C) The pressure is equal to the change in momentum of the fluid molecules as they collide with the surface of the object divided by the number of molecules and the surface area
    (D) The pressure is equal to the temperature of the fluid molecules divided by the time and surface area.
    (E) None of these.
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  2. #2  
    KJW
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    MODERATOR NOTE: This looks like homework, so I moved it to the "Homework Help" forum. Generally, we don't do people's homework for them, though we are willing to help provided that the person requesting help has made some effort. Therefore, I shall ask you which option you think the answer is?
    A tensor equation that is valid in any coordinate system is valid in every coordinate system.
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  3. #3  
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    Quote Originally Posted by zhenis View Post
    20. Which of the following describes fluid pressure against a flat surface?

    (A) The pressure is equal to the change of momentum of the fluid molecules as they collide with the surface of the object divided by the time and the surface area.
    (B) The pressure is equal to the change in kinetic energy of the fluid molecules as they collide with the surface of the object divided by the time and the surface area.
    (C) The pressure is equal to the change in momentum of the fluid molecules as they collide with the surface of the object divided by the number of molecules and the surface area
    (D) The pressure is equal to the temperature of the fluid molecules divided by the time and surface area.
    (E) None of these.
    All of the answers have "divided by ...... and the surface area." Pressure can have units of force per unit of area. eg pounds per square inch, or the metric equivalent Newtons per square meter. Wiki on Pressure
    The SI unit for pressure is the pascal (Pa), equal to one newton per square metre (N/m2 or kgm−1s−2).
    .

    But the question was "Which of the following describes fluid pressure against a flat surface? " So I'm left wondering is that asking for total pressure or pressure per unit area?
    B,C and D seem wrong but A is possible so it is either A or E?
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