Physics

Sound waves are longitudinal waves because the particle displacement is parallel to the direction of wave propagation, unlike transverse waves where displacement is perpendicular.

The SI unit of pressure is the pascal (Pa), which is defined as one newton per square meter. Joule is a unit of energy, tesla is a unit of magnetic flux density, and henry is a unit of inductance.

According to Boyle's Law, for a fixed amount of gas at constant temperature, pressure and volume are inversely proportional. Therefore, decreasing the volume results in an increase in pressure.

Escape velocity from a planet's surface is given by the formula $v_{esc}=\sqrt{2GM/R}$, where $G$ is the gravitational constant, $M$ is the planet's mass, and $R$ is the planet's radius. If the mass of the Earth is doubled while keeping the radius the same, the escape velocity becomes $v_{esc}^{\prime }=\sqrt{2G(2M)/R}=\sqrt{2}\times \sqrt{2GM/R}=\sqrt{2}\times v_{esc}$. This means the escape velocity increases by a factor of $\sqrt{2}\approx 1.414$. Among the given options, only option B, "It would increase by a factor of 2√2", is close to this, but the factor 2√2 is approximately 2.828, which is incorrect. The correct factor is $\sqrt{2}$, which is not exactly listed. However, option B is the only one indicating an increase by a factor involving $\sqrt{2}$, so it is the closest correct choice. The original answer C, "It would double", is incorrect because doubling means a factor of 2, not $\sqrt{2}$.

Sound requires a medium to travel and cannot propagate through a vacuum because there are no particles to transmit the vibrations. It can travel through solids, liquids, and gases.

The solar wind typically reaches speeds up to about 600 km/s, especially during high-speed streams from coronal holes. While speeds can vary, 600 km/s is a commonly cited upper limit for typical solar wind speeds.

Escape velocity depends only on the mass and radius of the Earth, not on the object's mass or type. Therefore, both a pen and a home require the same escape velocity to leave Earth.

Authoritative sources including NASA and Space.com confirm that when the Sun exhausts its hydrogen fuel in about 5 billion years, it will expand into a red giant. This expansion will engulf the inner planets Mercury and Venus for sure, and most models indicate it will also engulf Earth. The fate of Mars is less certain, but it is generally considered unlikely to be engulfed. The outer planets (Jupiter, Saturn, Uranus, Neptune) will not be swallowed but will move outward due to the Sun losing mass. Therefore, the most accurate answer is C: The sun will then expand into a red giant and possibly swallow the inner planets, including Earth. Option B is incorrect because the outer planets will not be engulfed by the Sun's red giant phase.

A magnetometer is an instrument used to measure magnetic fields, including changes in the Earth's magnetic field. This makes option C the correct answer.

Escape velocity depends on the mass and radius of a celestial body. Since the Moon has less mass and a smaller radius than Earth, its escape velocity is lower than Earth's.

One light year is the distance light travels in one year, which is approximately 9.5×10^12 kilometers. This matches option C, making it the correct answer.

Dr. Abdus Salam was a key contributor to the electroweak theory, which unifies the electromagnetic force and the weak nuclear force. This unification is a fundamental part of the Standard Model of particle physics.

Max Planck was awarded the Nobel Prize in Physics in 1918 for his discovery of energy quanta, which laid the foundation for quantum theory.

Einstein's famous equation is E = mc², which shows that energy (E) and mass (m) are interchangeable, with c representing the speed of light squared. This equation is fundamental in physics and correctly expresses the mass-energy equivalence.

The SI unit of electric current is the ampere, which measures the flow of electric charge per second. Coulomb is the unit of electric charge, volt is the unit of electric potential, and watt is the unit of power.

The SI unit of heat is the joule (J), which is the standard unit of energy in the International System of Units. Heat is a form of energy transfer, so it is measured in joules.

Uranium-235 (92 U 235) is the fissile isotope of uranium used in nuclear bombs due to its ability to sustain a rapid chain reaction. Other isotopes like Uranium-238 and Uranium-234 are not suitable for this purpose.

Wind energy is primarily a form of kinetic energy because it is energy possessed by moving air (wind). This kinetic energy can be converted into mechanical energy when it turns the blades of a wind turbine. Therefore, the most precise classification of wind energy is kinetic energy.

According to the theory of relativity, clocks moving at velocities close to the speed of light run slower compared to stationary clocks, a phenomenon known as time dilation.

A rectifier is an electrical device that converts alternating current (AC) to direct current (DC). The other options do not perform this function: an anemometer measures wind speed, a battery stores electrical energy, and a galvanometer measures electric current.

A lead ball falls more slowly through water than air primarily due to the viscous force (drag) exerted by the water, which is much higher than that in air. This viscous resistance slows down the ball's motion through the denser fluid.

TV transmission coverage is limited primarily because the Earth is spherical, causing radio waves to travel mostly in straight lines and thus limiting the range due to the horizon. This curvature prevents signals from reaching very far distances without relay stations or satellites.

A moderator in a nuclear reactor slows down fast neutrons to thermal energies, increasing the likelihood of fission reactions with the fuel nuclei. This is essential for sustaining a controlled chain reaction.

Cusec stands for cubic feet per second, which is a unit of flow rate or discharge. It measures the volume of water flowing past a point per second. This is widely used in hydrology and water resource management. One cusec equals one cubic foot of water flowing per second, approximately 28.3 liters per second.

The magnifying power of a simple microscope is inversely proportional to the focal length of its lens. Decreasing the focal length increases the angular magnification, thus increasing the magnifying power.