Question

Consider an object that floats in water but sinks in oil. When object floats in water, half of it submerged. If one slowly poured oil on the top of the water surface so that it completely cove the object, the object

• A. Moves up
• B. Stops in the same place
• C. Moves down
• D. Data insufficien

Answer 1

The correct option is A Moves up

let volume of block=$v$

let density of oil $={\rho }_0$

density of water $=\rho$

Initial Buoyant force on block $=\frac{\rho v}{2}g$

when oil is added on top;

final bouyant force $=\rho \frac{v}{2}g+\frac{{\rho }_{0}vg}{2}$

As you can see, overall force on block

has increased. Therefore block will

move upwards