Question

Figure shows a weigh-bridge, with a beaker P with water on
one pan and a balancing weight R on the other. A solid ball
Q is hanging with a thread outside water. It has volume 40
cm³ and weighs 80 g. If this solid is lowered to sink fully in
water, but not touching the beaker anywhere, the balancing
weight R' will be
(a) same as R (b) 40 g less than R
(c) 40 g more than R (d) 80 g more than R

Answer 1

Explanation:

Buoyancy force on sphere will B=40×1×g

Now thrust due to this buoyancy on water is B or

Mass increased due to this thrust is m=B/g=40g.

Now the balancing weight will be 40g more than R , remaining weight of sphere is supported by tension .