Question

A wooden block, with a coin placed on its top, floats in water as shown in fig. The distance $l$ and $h$ are shown there. After some time the coin falls into the water. Then

• A. $l$ decreases and $h$ increases
• B. $l$ increases and $h$ decreases
• C. both $l$ and $h$ increases
• D. both $l$ and $h$ decreases

Answer 1

The correct option is D both $l$ and $h$ decreases

Density of coin is more, so it was applying considerable force on wood before falling in water. But once it falls, wood can't apply same force alone, so wood will move a little up, as a result $l$ will decrease.
When coin falls in water wood goes up, displaced volume decreases and coin has high density, it's volume is low and it doesn't displace liquid that much.
As a result $h$ will also decrease.