Question

3.
You are provided with a hollow iron ball A of volume
15 cm and mass 12 g and a solid iron ballB of mass 12 g.
Both are placed on the surface of water contained in a
large tub. (a) Find upthrust on each ball. (b) Which ball
will sink ? Give reason for your answer. (Density of iron
= 8.0 g cm )​

Answer 1

Answer:

You have Selena Physics class 9 book.

Explanation:

Volume of Ball A = 15cm³

Volume of water displaced by A = 15cm³

Upthrust = Weight of 15 cm³ of water

Density of water = mass / volume

1g/cm³ = mass / 15cm³

mass = 15g

Upthrust = 15gf or 150 N

Now, the balls are just placed on water so you have to calculate the

upthrust for submerged part of Ball A for which upthrust = weight of body = 12 gf or 120 N

For ball B,

mass = 15g

density = 8g/cm³

volume = m/d

= 1.5cm³

As you calculated the upthrust for A, calculate for B and you get 1.5gf or 15 N which is much less than the weight so boy will sink.

The reason why we took upthrust = weight of Ball A and not B is that in Ball A, we took its density to determine it will float or not and then we calculated the upthrust for submerged part.

Answer 2

hope hope it is helpful