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

The correct option is C 650 g

Upthrust on ball = weight of displaced water
$=V\sigma g=\frac{m}{\rho }\sigma g=\frac{40}{0.8}\times 1\times g=50gDyneor50gm$
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.