Railway Science (Physics-Fluid Mechanics)

Total Questions: 12

1. If you fill a glass completely with water and ice and the ice melts completely, what will happen? [[RRB Group D 01/10/2018 (Afternoon)]]

Correct Answer: (c) The water level will remain the same
Solution:

According to Archimedes, floating material displaces water equal to its weight. As floating ice melts, the water level remains unchanged because dissolved ice retains the same volume.

2. If an object sinks then the buoyancy exerted by the liquid on the object will be _______. [ [RRB Group D 09/10/2018 (Afternoon)]]

Correct Answer: (c) less than the weight of the object
Solution:

The upward force exerted by a liquid on a body when immersed in a liquid is known as buoyant force. When an object is floating in a liquid, the buoyant force exerted by the liquid on the object is equal to the weight of the object. This principle is known as Archimedes' principle.

3. When a body is completely or partially immersed in a fluid, a force is applied on it in the upward direction, which is equal to the weight of the fluid displaced by that body. By which rule is this explained? [[RRB Group D 15/10/2018 (Morning)]]

Correct Answer: (a) Archimedes' principle
Solution:

This principle explains why objects float or sink in fluids and is used to determine the buoyant force acting on objects submerged in fluids. Lenz's law is related to electromagnetic induction. Pauli's exclusion principle is related to the behavior of electrons in atoms. Faraday's law of electrolysis is related to equivalent weight of the electrolyte.

4. Which of the following factors depends on the resultant of buoyancy force acting on an object in a given fluid? [[RRB Group D 16/10/2018 (Afternoon)]]

Correct Answer: (c) Density of the liquid and volume of the object immersed in it.
Solution:

This is the upward force exerted by a fluid on an object immersed in it. It arises due to the pressure difference between the top and bottom of the object caused by the fluid's weight.

5. A stone is tied to a spring balance. Under which of the following conditions the reading on spring balance will show the least weight? [[RRB Group D 16/10/2018 (Evening)]]

Correct Answer: (b) When the stone is completely submerged in the water in a beaker.
Solution:
When an object is submerged in a fluid, it experiences an upward force known as the buoyant force. This force is equal to the weight of the fluid displaced by the object. Hence, the body experiences least weight.

6. The density of an iron nail is __________ the density of water. [[RRB Group D 22/10/2018 (Morning)]]

Correct Answer: (a) more than
Solution:

This is because the density of an iron nail is about 7.8 g/cm³ while the density of water is 1 g/cm³3 at 25 °C. Density is the ratio of mass to volume, and iron has more mass than water for the same volume. Therefore, iron is denser than water and sinks in it.

7. In liquids, a small fraction of particles at the surface have : [ [RRB Group D 25/10/2018 (Morning)]]

Correct Answer: (b) more kinetic energy
Solution:

At a given temperature in any gas, liquid or solid, there are particles with different amounts of kinetic energy. In the case of liquids, a small fraction of particles at the surface, having higher kinetic energy, is able to break away from the forces of attraction of other particles and gets converted into vapour. This phenomenon of change of liquid into vapours at any temperature below its boiling point is called evaporation.

8. Ice floats on water because its density is: [[RRB ALP Tier - I (20/08/2018) Afternoon]]

Correct Answer: (c) less than water
Solution:

Any substance that has a lower density in its solid state than in its liquid state will float. Density is the substance's mass per unit of volume. SI unit kg/m³. Formula ρ = m/V, where ρ is the density, m is the mass of the object and V is the volume of the object.

9. What is the upward force exerted by water called? [[RRB ALP Tier - I (21/08/2018) Morning]]

Correct Answer: (b) Buoyant force
Solution:

Archimedes principle: When a body is immersed in a liquid, an upward thrust equal to the weight of the liquid displaced, acts on it. Apparent weight = actual weight − buoyant force = mg − ρgV, where m = mass of the object, ρ = density of the fluid, g = acceleration due to gravity and V = volume of liquid displaced by the object.

10. What is the physical state of water at 12 °C? [ [RRB ALP Tier - I (29/08/2018) Afternoon]]

Correct Answer: (a) Liquid
Solution:

Below zero degrees (32 degrees Fahrenheit), Water becomes ice and above 100 degrees (212 degrees Fahrenheit) it becomes gas. Properties of Water (H2O, it is formed by the covalent bond of hydrogen and oxygen atoms) - Three states water (solids, liquids, and gas), has a polar nature, Amphoteric in Nature (react both as a base and as an acid), Solvency of Water (Universal solvent due to high dielectric constant).