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Concepts Of Physics MCQ Edition [Volume 1]PhysicsFluid Mechanics

Given the equations P = _ S 0 F S and P₁ - P₂ = g z , which of the following statements applies to an elevator that is accelerating upward?

Options

  1. ABoth the equations are valid.
  2. BThe first equation is valid but the second is not.
  3. CBoth the equations are invalid.
  4. DThe second equation is valid but the first is not.

Correct answer

B. The first equation is valid but the second is not.

Step-by-step solution

The first equation P = _ S 0 F S represents the fundamental definition of pressure at a point. This definition is independent of the frame of reference and remains valid in an accelerating elevator. The second equation P₁ - P₂ = g z represents the hydrostatic pressure difference in a fluid at rest in an inertial frame. In an elevator accelerating upward with an acceleration a , the effective acceleration due to gravity becomes g_ eff = g + a . The pressure difference in this non-inertial frame is given by P₁ - P₂ =

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