Question

A vessel with water is placed on a weighing pan and reads 600 g. Now a ball of 40 g and density 0.80 g/cc is sunk into the water with a pin as shown in fig. keeping it sunk. The weighing pan will show a reading

• A. 600 g
• B. 550 g
• C. 650 g
• D. 632 g

Answer 1

Answer: (C)

650 g

Answer 2

Upthrust on ball = weight of displaced water

$= V \sigma g = \left( \frac { m } { \rho } \right) \sigma g$ Dyne or 50 gm

As the ball is sunk into the water with a pin by applying

downward force equal to upthrust on it.

So reading of weighing pan = weight of water + downward

force against upthrust

= 600 + 50 = 650 gm.