Mechanical Physics — Part 1 MCQs with Explanations

Correct Answer: B: does not change Here's why the water level doesn't change when ice floating in water melts: * Archimedes' Principle: An object floating in water displaces its own weight of water. * Ice's Weight: The weight of the ice is exactly equal to the weight of the water it displaces when floating. * Melting Ice: When the ice melts, it turns into water. * Volume of Melted Ice: The volume of water produced by the melted ice is exactly the same as the volume of water the ice displaced when it was floating. * Conclusion: Because the melted ice contributes the same volume as the water it initially displaced, the water level remains the same .

The correct answer is A: requires larger deforming force Here's why: Elasticity refers to a material's ability to return to its original shape after a force is applied and then removed. A material is considered *more* elastic if it resists deformation more strongly. Think of it this way: Imagine stretching both a steel rod and a rubber band. The steel rod needs much more force to stretch even a little bit. The rubber band stretches easily with much less force. Therefore, steel is more elastic because it requires a larger deforming force to change its shape. Option B is incorrect: Steel can be deformed. Option C is incorrect: Steel is not easily deformed. Option D (hardness) is related to resistance to scratching or indentation, not elasticity (resistance to deformation and return to original shape).

The correct answer is A: adhesive force . Let's break down why: Adhesive force is the attraction between different types of molecules. Think of it like glue! The chalk sticks to the blackboard because of this attraction. Cohesive force is the attraction between the same type of molecules. This is what holds the chalk together as a solid, not what makes it stick to the board. Surface tension is the property of a liquid that makes its surface behave like a stretched membrane. It's not really relevant to chalk and blackboards. Viscosity is a fluid's resistance to flow. Think of honey versus water. Again, not relevant here. So, the adhesive force is the key property that allows the chalk to stick to the blackboard and leave a mark.

Let's break down this question about fluids (like water) in a cup when they're not moving (at rest). Statement 1: Pressure is same at all the points in the fluid. This isn't quite right. While the pressure is uniform *horizontally* at a given depth, it increases with depth due to the weight of the fluid above. So, this statement is partially correct but not entirely true in general. Statement 2: Pressure is exerted on the walls. This is absolutely correct. The fluid pushes against the walls of the cup. Think of it like tiny particles constantly bumping into the walls. Statement 3: Pressure exists everywhere in the fluid. This is also correct. Pressure isn't just on the walls; it's throughout the entire fluid. Imagine a tiny bubble inside the fluid; the fluid is pushing on all sides of the bubble. Therefore, statements 2 and 3 are definitely true. Statement 1 is not entirely correct because it doesn't account for the pressure increase with depth. Now let's look at the options: A: 1 and 2 (Incorrect because 1 is not fully correct) B: 2 and 3 (Correct!) C: Only 1 (Incorrect because 1 is not fully correct, and other statements are also true) D: 1, 2 and 3 (Incorrect because 1 is not fully correct) So, the correct answer is Option B: 2 and 3

When a body floats in a liquid, the condition of equilibrium is given by weight of the body = weight of the liquid displaced . This relationship is based on Archimedes’ principle , which depends on the gravitational acceleration (g) . On taking the body and the liquid to the Moon , the value of g decreases equally for both the body and the displaced liquid. Since both the weight of the body and the buoyant force depend linearly on g , the ratio between them remains the same. Therefore, the fraction of the body immersed in the liquid does not change. The body will continue to float as before , with the same part immersed as it was on Earth. Hence, the correct answer is: The body will continue to float as before.

The key to understanding this lies in how water's density changes with temperature. Water has a unique property: Its density is maximum at 4°C. When water is at 4°C, it's at its densest. As the temperature increases from 4°C to 100°C, the density of water decreases . Archimedes' Principle: A body floats when the buoyant force (upward force exerted by the fluid) equals the weight of the body. The buoyant force depends on the volume of fluid displaced and the density of the fluid. Since the water density decreases when heated to 100°C, a larger volume of water needs to be displaced to provide the same buoyant force to support the body's weight. Therefore, more of the body will submerge to displace the necessary volume of the less dense (warmer) water. So, the correct answer is (C).

maximum at 4°C is the correct answer to “Density of water is”. This question is standard in competitive examination syllabi for Mechanical Physics.

if the body remains in deformed shape even after removal of the deforming force is the correct answer to “The body is called perfectly plastic body”. This question is standard in competitive examination syllabi for Mechanical Physics.

it is the ratio of force to area and both force and area are vectors is the correct answer to “Pressure is a scalar quantity because”. This question is standard in competitive examination syllabi for Mechanical Physics.

Due to exertion of surface tension by the molecules is the correct answer to “Why do water droplets always take a round shape when dropped onto plane surfaces”. This question is standard in competitive examination syllabi for Mechanical Physics.

Solid is the correct answer to “In which situation the molecular attraction is very strong”. This question is standard in competitive examination syllabi for Mechanical Physics.

Volume is the correct answer to “The force of buoyancy depends on the density and . . . . . . . . of the liquid displaces.”. This question is standard in competitive examination syllabi for Mechanical Physics.

$$\frac{{2{\rho _1}{\rho _2}}}{{{\rho _1} + {\rho _2}}}$$ is the correct answer to “If two miscible liquids of same volume but different densities ρ 1 and ρ 2 are mixed, then the density of the mixture is given by”. This question is standard in competitive examination syllabi for Mechanical Physics.

(A) is true, but (R) is false is the correct answer to “Assertion (A): An iron ball floats on mercury but gets immersed in water. Reason (R): The specific gravity of iron is more than that of mercury.”. This question is standard in competitive examination syllabi for Mechanical Physics.

greater in the tube of smaller diameter is the correct answer to “Two capillary tubes of different diameters are dipped in water. The rise of water is”. This question is standard in competitive examination syllabi for Mechanical Physics.

The smaller bubble will become smaller and bigger will become bigger is the correct answer to “If two bubbles of soap of different diameter come in contact with a tube, then what will happen”. This question is standard in competitive examination syllabi for Mechanical Physics.

Boyant force is the correct answer to “What is the upward pressure generated by an object being placed on a fluid”. This question is standard in competitive examination syllabi for Mechanical Physics.

surface tension is the correct answer to “Soap bubble attains spherical shape due to . . . . . . . .”. This question is standard in competitive examination syllabi for Mechanical Physics.

Specific gravity of the needle is greater than that of water displaced by it is the correct answer to “A needle sinks in water whereas a ship made of iron floats on it because”. This question is standard in competitive examination syllabi for Mechanical Physics.

Capillary action is the correct answer to “How does a blotting paper absorbing ink”. This question is standard in competitive examination syllabi for Mechanical Physics.

2 is the correct answer to “Consider the figure of a fountain with four holes, given below. Which one of the holes in the fountain will throw the water farthest”. This question is standard in competitive examination syllabi for Mechanical Physics.

a-2, b-3, c-1, d-4 is the correct answer to “Match the columns. Column I Column II a. Linear strain 1. Change in the shape without changing its volume b. Volumetric strain 2. Change in length alone c. Shearing strain 3. Change in volume d. Young's modulus 4. Ratio of normal stress to longitudinal strain”. This question is standard in competitive examination syllabi for Mechanical Physics.

Surface tension is the correct answer to “An iron needle floats on the surface of water due to”. This question is standard in competitive examination syllabi for Mechanical Physics.

Less than the weight of the object is the correct answer to “When an object sinks, the up thrust of the fluid on the object is:”. This question is standard in competitive examination syllabi for Mechanical Physics.

surface tension is the correct answer to “Kerosene oil rises up in the wick of lantern because of”. This question is standard in competitive examination syllabi for Mechanical Physics.

The pressure depends on the height of liquid column is the correct answer to “A liquid is kept in a glass beaker. Which one of the following statements is correct regarding the pressure exerted by the liquid column at the base of the beaker”. This question is standard in competitive examination syllabi for Mechanical Physics.

Upthrust is the correct answer to “What is the force acting perpendicular to plane”. This question is standard in competitive examination syllabi for Mechanical Physics.

1 and 2 is the correct answer to “Consider the following statements. 1. The SI unit of young's modulus of elasticity is N/M 2 . 2. The reciprocal of the bulk modulus of the material of the body is called the compressibility of that material. 3. Compressibility of gases is very small. Which of the statements given above are correct”. This question is standard in competitive examination syllabi for Mechanical Physics.

The density of water is maximum at 4°C is the correct answer to “The surface of a lake is frozen in severe winter, but the water at its bottom is still liquid. Why? Following are some options”. This question is standard in competitive examination syllabi for Mechanical Physics.

Stormy weather is the correct answer to “A sudden fall in barometer reading indicates that the weather will be”. This question is standard in competitive examination syllabi for Mechanical Physics.

Rising of water from the roots of a plant to its foliage is the correct answer to “For which one of the following capillarity is not the only reason”. This question is standard in competitive examination syllabi for Mechanical Physics.

Increased in size is the correct answer to “When an air bubble at the bottom of lake rises to the top, it will”. This question is standard in competitive examination syllabi for Mechanical Physics.

Both 1 and 2 is the correct answer to “Consider the following statements. 1. The viscosity of a gas increases with rise in temperature. 2. The viscosity of the liquid falls very rapidly with rise in temperature. Which of the statement(s) given above is/are correct”. This question is standard in competitive examination syllabi for Mechanical Physics.

More than outside is the correct answer to “What is the pressure inside the aircraft cabin at altitude”. This question is standard in competitive examination syllabi for Mechanical Physics.

decreases is the correct answer to “The surface tension of water on adding detergent to it”. This question is standard in competitive examination syllabi for Mechanical Physics.

infinite is the correct answer to “The Young's modulus for perfectly rigid body is”. This question is standard in competitive examination syllabi for Mechanical Physics.

Theory of Archimedes is the correct answer to “The speed increases of ships is based on-”. This question is standard in competitive examination syllabi for Mechanical Physics.

Surface tension is the correct answer to “A drop of a fluid is combined because the attraction of its particles minimizes its possible area. This phenomenon is called-”. This question is standard in competitive examination syllabi for Mechanical Physics.

thickness, its diameter and its material is the correct answer to “The spring constant of a spring depends on its”. This question is standard in competitive examination syllabi for Mechanical Physics.

Viscosity is the correct answer to “The friction in liquids is called:”. This question is standard in competitive examination syllabi for Mechanical Physics.