In this question (b) , I was not able to understand why the upward thrust on the flat surface of the hemisphere will be piR^3, because the "2/3 pi R^3" amount of water has been occupied by the hemisphere itself... and hence the upward thrust on the flat surface should have been equal to the sum of vertical component of force exerted on the curved surface area of hemisphere and the weight of the hemisphere..... So if anyone could clear this doubt it will be helpfull..
Could also tell me why there will be no side thrust on the hemisphere?