Search Previous Year Questions

The correct answer is Just before it touches the ground.

Key Points

• When an object reaches the ground it has its maximum value of kinetic energy just before touching the ground.
• Since kinetic energy + potential energy = Constant, so on reaching the ground, the potential energy of an object becomes zero.
• So eventually, the kinetic energy on reaching the ground becomes maximum.

Additional Information

• Kinetic energy is the work needed to accelerate a body of a given mass from rest to its stated velocity.
• K.E. = $1\over2$ mv², where, m= mass of the body, v= velocity of the given group.
• Potential energy is stored energy that depends upon the relative position of various system parts.
• P.E. = mg h, where, m= mass of the body, g= gravitational acceleration, h= height.
• When the stone was at top of the roof it has P.E. = maximum, K.E.= zero. Because the stone was in idle condition so velocity, v=0, K.E.=0.
• Just after the stone is dropped, P.E. is started reducing, and the velocity is increasing, which in turn increases its K.E.
• When the stone is just halfway, K.E. and P.E. just become half of their actual values.
• When the stone touches the ground, its velocity v=0, so K.E. =0, and P.E. again get restored to its original value.
• The law of conservation of energy states that energy can neither be created nor destroyed, it transforms from one form to another.
• So in the course of the stone dropped from the roof of a house to its reaches at the ground, K.E. and P.E. transform between each other.
• But every time, K.E. + P.E. = Total energy = Constant must be maintained.

The correct answer is Pune.

Key Points

• National Institute of Virology
• It was established at Pune, Maharashtra in 1952 as Virus Research Centre (VRC).
• It was an outcome of the global programme of the Rockefeller Foundation (RF) of the USA for investigating the Arthropod-Borne viruses.
• The research activities of the Institute are coordinated by a Scientific Advisory Committee (SAC) consisting of eminent scientists.
• The Institute was designated as one of the collaborating laboratories of the World Health Organization (WHO) in 1967 and it started functioning as the regional centre of the WHO for South-East Asia for arbovirus studies from 1969.
• In 1995 it has been redesignated as the WHO Collaborating Centre for Arbovirus and Haemorrhagic Fever Reference and Research and Rapid Diagnosis of Viral Diseases.
• Director- Prof. Priya Abraham

The correct answer is Specific Gravity.

The correct answer is Speed is constant.

Key Points

• Circular motion is a movement of an object along the circumference of a circle or rotation along a circular path.
• The distance and displacement are different at every instance at any particular point of time.

Confusion Points

• While the speed is a scalar quantity, in uniform motion, it remains constant.
• As, Velocity is a vector quantity, and the direction of movement changes continuously, velocity changes continuously.
• Due to this, the object is in accelerated motion.

Important Points

About the Circular Motion:

• As the direction of the velocity changes at every instant, it is an accelerated motion.
• During the motion, the particle repeats it's paths along the same trajectory.
• Thus the motion is periodic.

Uniform Circular Motion:

• During circular motion, if the speed of the period remains constant, it is a Uniform Circular Motion. Hence option 4 is correct.

The correct answer is Gamma rays.

• Gamma rays consist of high-energy waves that can travel great distances at the speed of light and generally have a great ability to penetrate other materials.
• For that reason, gamma rays (such as from cobalt-60) are often used in medical applications to treat cancer and sterilize medical instruments.

Important Points

• Ultraviolet (UV) light has shorter wavelengths than visible light.
• The wavelength range is from 100-400 nm.
• Although UV waves are invisible to the human eye, some insects, such as bumblebees, can see them.
• This is similar to how a dog can hear the sound of a whistle just outside the hearing range of humans.
• These invisible rays that are part of the energy that comes from the sun, that can burn the skin and cause skin cancer.
• It is widely used in industrial processes and in medical and dental practices for a variety of purposes, such as killing bacteria, creating fluorescent effects, curing inks and resins, phototherapy, and suntanning.
• Light radiates from a source in waves.
• Each wave has two parts: an electric part, and a magnetic part. That's why light is called Electromagnetic Radiation.
• Visible light is usually having wavelengths in the range of 400–700 nm (4.00 × 10⁻⁷ to 7.00 × 10⁻⁷ m), between the infrared and the ultraviolet.
• X-rays have much higher energy and much shorter wavelengths than ultraviolet light.
• X-rays have very small wavelengths, between 0.01 to 10 nanometers.
• The use of x-rays is checking for fractures (broken bones), chest x-rays can spot pneumonia. Mammograms use x-rays to look for breast cancer.

Additional Information

• X-rays were first observed and documented in 1895 by German scientist Wilhelm Conrad Roentgen.
• Radio waves, television waves, and microwaves are all types of electromagnetic waves.

CONCEPT:

Storage of Sodium

• Sodium is a highly reactive alkali metal.
• It reacts vigorously with oxygen and moisture present in air, forming sodium oxide and sodium hydroxide.
• This reaction can lead to the ignition of sodium, as it generates heat and hydrogen gas, which is flammable.

EXPLANATION:

• To prevent sodium from reacting with air or moisture, it is stored under a non-reactive liquid like kerosene.
• Kerosene acts as a protective barrier, isolating sodium from air and water, thereby preventing unwanted reactions.

Additional Information

• Absolute alcohol can react with sodium, forming hydrogen gas and sodium alkoxide.
• Petrol is highly volatile and flammable, which increases the risk of fire when combined with sodium.
• CHCl₃ (chloroform) is not commonly used for sodium storage and may not effectively isolate sodium from air and moisture.

Therefore, sodium is usually kept in kerosene to ensure its safe storage and prevent reactions with air and moisture.

The correct answer is Changing the shape of the body.

Key Points

• The rate of change of displacement is called velocity.
• Velocity is a vector quantity, which has both magnitude and direction.
• SI Unit of velocity is m/sec.
• It may be positive or negative.
• If a body is moving on a circular then after completing one complete cycle, its average velocity is zero.
• The velocity of an object is the speed of an object moving in a definite direction.
• Velocity changes with the speed and direction of motion of the body.
• Changing the shape of the body will not affect the velocity of the body.

The correct answer is the Microwave.

Key Points

• A microwave oven uses microwaves to heat food.
• In the case of microwave ovens, the commonly used radio wave frequency is roughly 2,500 megahertz (2.5 gigahertz).
• Radio waves in this frequency range absorbed by water, fats, and sugars. When they are absorbed they are converted directly into atomic motion or vibration.
• Therefore heavy motion or vibration is converted into heat.

Important Points

• Microwaves are not absorbed by most plastics, glass, or ceramics.
• The frequency of the Microwave equals the resonance frequency of water. Therefore foods could be heated up by the oscillation of water molecules.

Additional Information

• An Electric heater, Electric blub (with filament), Electric iron is the electrical device that converts an electric current into heat.
• They working on the principle of the Joule heating effect.
• An electric current passing through a resistor will convert that electrical energy into heat energy.

The correct answer is calcium and phosphorus.

Key Points:

• The structure that holds the body up is made of bone.
• Additionally, it supports the body's major organs and anchors the muscles.
• It is a solid, unyielding tissue.
• A dense matrix made of calcium and phosphate molecules contains the bone cells.
• A different kind of connective tissue called a ligament can join two bones together.
• This tissue is extremely flexible.
• Another form of connective tissue is the tendon, which links bones and muscles.

Additional Information:

• Tendons are fibrous tissues with little flexibility and tremendous strength.
• The cells of cartilage are widely spaced.
• Sugars and proteins make up the solid matrix.
• In addition to the nose, ear, trachea, and larynx, cartilage smoothes the surfaces of bones at joints.
• Areolar connective tissue can be found in the bone marrow, around blood vessels and nerves, and between the skin and muscles.
• It supports internal organs, fills empty space inside the organs, and aids in tissue restoration.

The Correct answer is Edwin Hubble.

Key Points 

• 'Expanding Universe'
• Edwin Hubble, an American astronomer, and was the first to prove that the universe is expanding.
• According to Expanding Universe theory, the universe is presently expanding.
• Hubble proved that there is a direct relationship between the speeds of distant galaxies and their distances from Earth.
• This is now known as Hubble’s Law.

Additional Information

• Black Hole
• It refers to a point in space where the matter is so compressed as to create a gravity field from which even light cannot escape.
• The concept was theorized by Albert Einstein in 1915 and the term ‘black hole’ was coined in the mid-1960s by American physicist John Archibald Wheeler.
• Usually, the black holes belong to two categories:
• One category ranges between a few solar masses and tens of solar masses. These are thought to form when massive stars die.
• The other category is supermassive black holes.
• These range from hundreds of thousands to billions of times that of the sun from the Solar system to which Earth belongs.
• In April 2019, the scientists at the Event Horizon Telescope Project released the first-ever image of a Black Hole (more precisely, of its shadow).
• The Event Horizon Telescope is a group of 8 radio telescopes (used to detect radio waves from space) located in different parts of the world.
• Gravitational waves are created when two black holes orbit each other and merge.