Question

A wooden block and a metal coin are connected by a string as shown in figure.Both have the same volume and both are placed in a beaker of water. Now the beaker is given acceleration towards right, then the string will tilt towards.

A. Right
B. Nowhere
C. Left
D. Either left or left

Answer 1

We will take into consideration the density of the coin and the block.Then we will use these densities to check what the string would feel initially. Finally, we will check what would happen to the tilt of the string when the whole setup is accelerated rightwards.

Complete answer:
Generally the density of a metal coin is higher than water. Due to this knowledge, we can say that the metal coin will sink and stay immersed in water.Also, we know that the density of the wooden block is nearly equal to the density of water. Thus, we can say that the wooden block will float inside the water.

Thus, initially we can clearly say that the coin will sink totally in the water and the wooden block will float inside the water thus the string will stay stretched initially. Now, when the beaker is accelerated towards the right and thus a force is acted on the beaker in the rightwards direction.

Now, the system inside will feel a force in a direction opposite to the force or the acceleration acting on the beaker. This opposite force is known as pseudo force. Also, we know that the coin’s density is higher than the water in the beaker thus only the wooden block will feel the pseudo force. Thus, the coin will move with the beaker whereas the wooden block will move towards the left. Thus the string will tilt towards left.

Hence, the correct answer is C.

Note: A pseudo force is not an actual force acting on a system. It is an imaginary force which acts as a result of a force which is acting on the larger system of which the considered system is a part of. The density comparison we took here is factually based. Though the densities are not given here, we have to have a basic knowledge of different objects. At least an idea of the value of the density if the exact value is not known.