Question

An iron block and a wooden block are positioned in a vessel containing water as shown in the figure. The iron block $(1)$ hangs from a massless string with a rigid support from the top while the wooden block $(2)$ floats being tied to the bottom through a massless string. If now the vessel starts acceleration towards right

A. Iron block gets deflected towards the right
B. Wooden block gets deflected towards right
C. Iron block gets deflected towards left
D. Wooden block gets deflected towards left

Answer 1

When attempting questions like the one given to us above, keep in mind the various concepts surrounding buoyant force and its effects on objects submerged in water. Keep in mind how the buoyant force is different or similar to other types of forces and how all are affected by acceleration.

Complete step by step answer:
Before we start attempting this question, try to understand what buoyant force actually means. Buoyancy is the force which helps cause objects to float. It is the force exerted on an object that is partly or wholly immersed in a fluid, which in our case is water. For easy communication we call this force buoyant force.
For simpler understanding, let’s call buoyant force as the upward force applied by water on the object when it is put in or submerged in water.
Now when we talk about buoyant force, we also keep in mind the Archimedes principle related to buoyant force. Archimedes' principle was discovered by the famed Greek mathematician Archimedes. It states that any body completely or partially submerged in a fluid which can be liquid or gas, at rest is acted upon by an upward or buoyant force, magnitude of which is equal to the weight of the fluid displaced by the body. The volume of displaced fluid is equivalent to the volume of an object fully immersed in a fluid or to that fraction of the volume below the surface for an object partially submerged in a liquid.
In the question given to us, when the vessel starts accelerating towards the right, the iron block suspended in the vessel also gains an acceleration added with the buoyant force it experiences while being inside the body submerged in water. So when the vessel accelerates towards the right, the iron block also gets deflected towards the right.

Hence option $(A)$ is the correct answer.

Note:
When we talk about buoyancy, there are three types of buoyant forces; positive, negative and neutral. Positive force is when the object is lighter than fluid and hence floats in fluid. Negative force is when an object is heavier and sinks in fluid. Neutral force is when the volume of fluid displaced is equal to the volume of the object.