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?

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=vρ1g−vρg=vgρ1−ρWhen the lift is moving upwards with acceleration a, the tension in the string is T=vρ1−ρ(g+a) From Eqs. (i) and (ii), T=T0(1+a/g)