Physics

Newton's first law of motion states that an object will remain at rest or in uniform motion unless acted upon by an external force, which is the concept of inertia.

The composition of vectors involves combining vectors to form a resultant vector, typically through addition. The reverse process is the resolution of vectors, which breaks a single vector into its component vectors.

Resistivity is a material property and does not depend on the dimensions of the wire. Cutting the wire into parts changes the resistance but not the resistivity, which remains the same for each part.

The drift velocity of free electrons in a wire is directly proportional to the applied potential difference (voltage). Therefore, if the potential difference is doubled, the drift velocity will also double.

A Wilson Cloud Chamber (Cloud Detector) is used to visualize the paths of charged particles, including visible rays, by creating condensation trails in supersaturated vapor. Geiger counters and solid state detectors detect radiation but do not visually show the path of rays.

When a body rotates about an axis passing through itself, the motion is called spin motion. Orbital motion involves rotation around an external point, rectilinear motion is straight-line motion, and translatory motion refers to movement without rotation.

Earth's average orbital speed around the Sun is approximately 30 km/s, which is the widely accepted and measured value.

A black body that emits radiation across the entire visible spectrum appears white because white light is a combination of all visible wavelengths. Therefore, the correct answer is White.

The antiparticle of the electron is the positron, which has the same mass as the electron but opposite charge. Protons, mesons, and neutrons are different particles and not the electron's antiparticle.

The linear velocity (v) of a point on a rotating object is related to its angular velocity (ω) and radius (r) by the formula v = rω. This means the linear speed increases with both the radius and the angular velocity.

A photon is a particle of light and always moves at the speed of light in vacuum, which is approximately 3 x 10^8 m/s. It cannot be at rest or move at any other speed such as the speed of sound.

Space waves travel in a straight line and are used for line of sight (LOS) communication, making them the correct choice. Cable waves and antenna waves are not standard terms for LOS communication waves.

The SI unit of time is the second, which is the standard unit used worldwide for measuring time intervals.

Moonlight takes approximately 1.3 seconds to travel from the Moon to the Earth because the average distance is about 384,400 km and light travels at about 300,000 km/s.

The 2017 Nobel Prize in Physics was awarded to Rainer Weiss, Kip Thorne, and Barry Barish for their decisive contributions to the LIGO detector and the first direct observation of gravitational waves. The prize specifically recognized the first direct detection of gravitational waves on September 14, 2015, by the LIGO Scientific Collaboration, which confirmed a major prediction of Einstein's general theory of relativity. The correct phrasing is 'First Observation of Gravitational Waves,' making option C the accurate choice.

The speed of sound in air at sea level and at room temperature is approximately 340 meters per second, which is the widely accepted standard value.

J.J. Thomson is credited with the discovery of the electron in 1897 through his cathode ray tube experiments, which demonstrated the existence of negatively charged particles smaller than atoms.

The speed of light in vacuum is approximately 300,000 kilometers per second (more precisely about 299,792 km/s), which matches option B. The other options are incorrect values.

The resistance of the heater coil is directly proportional to its length. Reducing the length by 10% decreases resistance by 10%. Since power P = V²/R (with constant voltage), a decrease in resistance causes an increase in power consumption. Therefore, power consumed increases by more than 10%.

The SI base unit for mass is the kilogram (kg), which is the internationally accepted standard unit for measuring mass. Other options like gram, pound, and ounce are units of mass but are not the SI base unit.

The current SI standard for the unit of time, the second, is defined based on the frequency of radiation emitted by the transition between two hyperfine levels of the ground state of the cesium-133 atom. Specifically, one second is defined as the duration of 9,192,631,770 periods of this radiation. Historically, krypton-86 was used for defining the meter, not the second. Therefore, among the given options, the closest and correct answer is B, although it should refer to cesium-133 rather than krypton-86. The other options (daily rotation of the earth, yearly revolution of the earth, and precision pendulum clock) are not the basis for the current SI definition of the second.

Sound waves are mechanical waves that require a medium to travel through and are not electromagnetic radiation. Red light and X-rays are types of electromagnetic radiation, and photons are the particles that make up electromagnetic radiation.

Magnetars are a type of neutron star characterized by extremely strong magnetic fields, much stronger than typical neutron stars. Quasars are active galactic nuclei, not neutron stars. 'Magneto' and 'Magnetta' are not recognized subclasses of neutron stars.

The color of the glow in a discharge tube depends on the gas inside it because different gases emit characteristic colors when excited by an electric discharge. The metal cathode or pressure can influence other factors but do not primarily determine the glow color.

A pulsar is a rapidly spinning neutron star that emits beams of electromagnetic radiation, primarily radio waves, which can be detected from Earth as pulses when the beam points toward us.