First slide
Pressure in a fluid-mechanical properties of fluids
Question

The tension in a string holding a solid block below the surface of a liquid (where ρliquid >ρblock ) as in shown in the figure is T0 when the system is at rest. Then what will be the tension in the string if the system has upward acceleration a?

Moderate
Solution

Let v be the volume of the solid block of density ρ. Let ρ1 be the density of water. Weight of body = vρg. When the body is immersed in water,
Tension in the string = Upward thrust - Weight of the body

T=vρ1gvρg=vgρ1ρ

When the lift is moving upwards with acceleration a, the tension in the string is T=vρ1ρ(g+a)

 From Eqs. (i) and (ii), T=T0(1+a/g)

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