CAIE A-Level Physics AS 4.3.3 Derive From the Definitions of Pressure and Density the Equation Questions

Explain upthrust as the upward force exerted by a fluid on an immersed object.

Exam points

Explain upthrust as the upward force exerted by a fluid on an immersed object.

[Maximum number: 3]

A beaker in air contains a liquid. The base of the beaker is in contact with the liquid and has area A, as shown in Fig. 4.1.

Fig. 4.1

The liquid has density $\rho$ and fills the beaker to a depth h.

By using the definitions of pressure and density, show that

p=\rho g h

where p is the pressure due to the liquid that is exerted on the base of the beaker and g is the acceleration of free fall.

$\rho=m / V$ or $\rho=m / A h$
p=F / A or p=W / A
appropriate algebra leading to $p=\rho g h$

e.g. $p=\rho A h g / A$ or $\rho V g / A$ or $\rho V g /(V / h)$ and (so) $p=\rho g h$

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CAIE A-Level Physics AS 4.3.3 Derive From the Definitions of Pressure and Density the Equation Questions question 1