Unit And Measurement — Part 1 MCQs with Explanations

Let's break down the options: Option A: Weight and Velocity - Velocity is measured in meters per second (m/s), not Newtons. Option B: Weight and Force - This is the correct answer. Option C: Weight and Mass - Mass is measured in kilograms (kg), not Newtons. Option D: Weight and Acceleration - Acceleration is measured in meters per second squared (m/s²), not Newtons. Newton's Second Law of Motion states that Force (F) = Mass (m) x Acceleration (a) . The unit of force derived from this equation is the Newton. Weight is a type of force , specifically the force of gravity acting on an object's mass. Therefore, weight is also measured in Newtons. Therefore, the correct answer is B: Weight and Force.

Why Option A is incorrect: Physical quantities are measurable by definition. If a property cannot be measured, it cannot be classified as a physical quantity. Why Option B is incorrect: Physical laws are expressed using physical quantities, but the quantities themselves are not defined by being expressible as a law. For example, mass, length, and time are physical quantities, but they are not laws in themselves. Why Option C is correct: Every physical quantity can be described completely with a numerical value (magnitude) and a suitable unit of measurement. For instance, 20 kg means "20" is the magnitude and "kg" is the unit—this fully represents the physical quantity (mass). Why Option D is incorrect: Since option B is not a defining characteristic, both B and C together cannot be correct. Only C correctly describes physical quantities. Conclusion: A physical quantity is fully defined by its magnitude and unit, so the correct answer is Option C .

a. Earthquake → 2. Seismograph A seismograph is an instrument used to detect and record seismic vibrations and waves produced by earthquakes . b. Altitude (Height) → 3. Altimeter An altimeter is an instrument used to measure the altitude or height of an object above a reference level, usually mean sea level . c. Electric current → 1. Ammeter An ammeter is an instrument used to measure the electric current flowing through a circuit . The SI unit of electric current is the ampere (A) . d. Resistance → 4. Ohm The ohm (Ω) is the SI unit of electrical resistance . Resistance is the opposition offered by a conductor to the flow of electric current. Thus, the correct matching is a-2, b-3, c-1, d-4 . Hence, Option A is the correct answer.

A hygrometer is an instrument used to measure the humidity of the air , that is, the amount of water vapour present in the atmosphere. Option A: Heat Incorrect. Heat is a form of energy and is measured using appropriate temperature or calorimetric methods, not a hygrometer. Option B: Humidity Correct. A hygrometer measures humidity , commonly expressed as relative humidity in percentage (%). Option C: Force Incorrect. Force is measured using a force meter or spring balance , and its SI unit is the newton (N) . Option D: Radiation Incorrect. Radiation is measured using instruments such as radiometers or radiation detectors , depending on the type of radiation. Hence, Option B — Humidity is the correct answer.

Let's understand this question about "Fundamental Quantities" . In Physics, we describe many things using physical quantities. These quantities are mainly divided into two types: 1. Fundamental Quantities 2. Derived Quantities Think of Fundamental Quantities as the absolute basic building blocks of physics. They are independent, meaning you cannot define them by using other physical quantities. There are seven fundamental quantities in the International System of Units (SI system): - Length - Mass - Time - Electric Current - Temperature - Amount of Substance - Luminous Intensity Derived Quantities , on the other hand, are quantities that are created by combining (multiplying or dividing) one or more fundamental quantities. Now let's look at our options to see which one is a fundamental quantity: Option A: Volume Volume is calculated as Length × Width × Height. Since Length, Width, and Height are all types of Length (which is a fundamental quantity), Volume is made up of length. So, Volume is a Derived Quantity . Option B: Time Time is one of the seven basic building blocks we listed above. You cannot break it down into other simpler physical quantities. So, Time is a Fundamental Quantity . Option C: Velocity Velocity is calculated as Distance / Time. Distance is a type of Length , and Time is a Fundamental Quantity . Since Velocity is made from Length and Time, it is a Derived Quantity . Option D: Force Force is calculated using Mass × Acceleration. Acceleration itself is (Velocity / Time), and Velocity is (Distance / Time). So, Force depends on Mass , Length (from Distance), and Time . Therefore, Force is a Derived Quantity . Based on our understanding, the only fundamental quantity among the choices is Time . The correct answer is Option B: Time .

A kilowatt-hour (kWh) is a unit of energy. It is the amount of energy consumed when a power of 1 kilowatt (1000 watts) is used for 1 hour (3600 seconds) . 1 kWh = 1000 W × 3600 s = 3.6 × 10 6 J Therefore, 2 kWh = 2 × 3.6 × 10 6 J = 7.2 × 10 6 J Hence, 2 kWh = 7.2 × 10 6 joules , so the correct answer is Option B .

The correct answer is Option B: 10 -4 cm . Here's why: Micron is another name for micrometer . The prefix " micro- " always means one millionth (1/1,000,000) or 10 -6 . So, 1 micron = 1 micrometer = 10 -6 meters. Now, we need to convert meters to centimeters. We know that 1 meter = 100 centimeters or 10 2 centimeters. Therefore, 1 micron = 10 -6 meters = 10 -6 * 10 2 centimeters = 10 -6+2 centimeters = 10 -4 centimeters. So, one micron represents a length of 10 -4 cm .

Option A: Time In classical or Newtonian physics, time is considered an absolute quantity . All observers measure the same time interval regardless of their state of motion. It does not depend on any reference frame in basic physics, which makes it the correct answer. Option B: Acceleration Acceleration is a relative quantity because it is the rate of change of velocity, and velocity itself depends on the observer’s frame of reference. Different observers may record different acceleration values depending on their motion. Option C: Velocity Velocity is highly relative since it directly depends on the chosen reference frame. For example, a person walking inside a moving train has a different velocity relative to someone inside the train compared to an observer standing outside on the platform. Option D: Momentum Momentum is defined as the product of mass and velocity. Since velocity is relative, momentum is also relative . Its value changes according to the observer’s frame of reference. Conclusion: Among the given quantities, the one which is not a relative quantity in classical physics is Time . Therefore, the correct answer is Option A: Time.

The correct answer is B: Pressure of gas . Let's break down why: Think of a manometer like a simple tool for comparing pressures. It usually involves a U-shaped tube filled with a liquid. Air pressure (Option A) : While manometers can *relate* to air pressure, they are specifically designed to measure the pressure of enclosed gases. Pressure of gas (Option B) : A manometer directly measures the pressure of a gas within a container or system. It works by comparing the gas pressure to a reference pressure (often atmospheric pressure). The difference in liquid levels in the U-tube tells us the pressure difference. Density of liquids (Option C) : Density is a measure of how much mass is in a given volume. Manometers don't directly measure density; instruments like hydrometers do that. Pressure of oil on the surface (Option D) : While pressure exists on the surface of a liquid like oil, a manometer isn't typically used for this specific measurement. Other sensors are more suitable for measuring surface pressures. In summary , a manometer is primarily used to measure the pressure of a gas by comparing it to a known reference pressure.

In Physics, we describe things using quantities. These quantities can be mainly of two types: 1. Scalar Quantities: These quantities only have a magnitude (a size or an amount). They don't have a specific direction. Example: If you say the temperature is 25 degrees Celsius, it's just a value, it doesn't point anywhere. 2. Vector Quantities: These quantities have both a magnitude (size) and a direction . Example: If you say you pushed a box with 10 Newtons of force to the right , you've given both the amount (10 Newtons) and the direction (to the right). Now let's look at the options in the question: Option A: Volume Volume tells you how much space something occupies (like how much water a bottle can hold). It's just a size, it doesn't have a direction. So, Volume is a scalar quantity . Option B: Mass Mass tells you how much 'stuff' an object is made of. It's just an amount, it doesn't point anywhere. So, Mass is a scalar quantity . Option C: Force Force is a push or a pull. When you push or pull something, you always do it in a specific direction with a certain amount of strength. For instance, you push a door open outward , or you pull a rope upward . Because Force has both magnitude (how strong the push/pull is) and direction, it is a vector quantity . Option D: Length Length tells you how long something is. It's just a size or a distance, it doesn't have a specific direction. So, Length is a scalar quantity . (Note: While 'displacement' is a vector quantity, as it involves both distance and direction from a starting point, 'length' or 'distance' itself is scalar). Therefore, the correct answer is Force because it is the only quantity among the options that has both magnitude and direction.

The prefix "kilo" in the metric system represents 1000. Therefore, 1 kilometer (km) is equal to 1000 meters (m). Hence, a distance of 1 km means 1000 m.

"Nano" is a prefix that means one billionth (1/1,000,000,000). A nanometer (nm) is therefore one billionth of a meter. We know that 1 meter (m) = 100 centimeters (cm) . So, 1 nanometer (nm) = (1/1,000,000,000) meter = (1/1,000,000,000) × 100 cm This simplifies to: 1 nm = 100 / 1,000,000,000 cm = 1 / 10,000,000 cm In scientific notation: 1 / 10,000,000 = 10⁻⁷ Therefore, 1 nanometer = 10⁻⁷ cm . ✔ Correct Answer: Option B – 10⁻⁷ cm

The question asks us to find the quantity with a different dimension compared to the others. Remember, dimension refers to the fundamental units (like mass, length, and time) that make up a physical quantity. Let's examine each option: Option A: Energy per unit volume Energy has dimensions of [ML 2 T -2 ] and volume has dimensions of [L 3 ]. So, energy per unit volume has dimensions of [ML 2 T -2 ]/[L 3 ] = [ML -1 T -2 ]. Option B: Product of voltage and charge per unit volume Voltage * charge = Energy,so Energy per unit volume and dimension is [ML -1 T -2 ] Option C: Angular momentum per unit mass Angular momentum is defined as Iω (moment of inertia * angular velocity). So, its dimensions are [ML 2 T -1 ]. Dividing by mass gives: [L 2 T -1 ] Option D: Force per unit area Force has dimensions of [MLT -2 ] and area has dimensions of [L 2 ]. So, force per unit area has dimensions of [MLT -2 ]/[L 2 ] = [ML -1 T -2 ]. Notice that Options A,B and D all have dimensions of [ML -1 T -2 ]. Option C, however, has dimensions of [L 2 T -1 ]. Therefore, the answer is Option C: Angular momentum per unit mass because its dimensions are different from the other three options.

Meter/second is the correct answer to “What is the SI unit of wave speed”. This question is standard in competitive examination syllabi for Unit And Measurement.

a-1, b-2, c-3, d-4 is the correct answer to “Match List-I with List-II and select the correct answer: List-I (Quantity) List-II (Units) a. High speed 1. Mach b. Wavelength 2. Angstrom c. Pressure 3. Pascal d. Energy 4. Joule”. This question is standard in competitive examination syllabi for Unit And Measurement.

a-3, b-1, c-2, d-4, e-5 is the correct answer to “Match the following. List-I List-II a. Joule 1. Current b. Ampere 2. Power c. Watt 3. Work d. Volt 4. Electric potential e. Calorie 5. Heat”. This question is standard in competitive examination syllabi for Unit And Measurement.

Resistance is the correct answer to “Ammeter : Electric current :: Ohmmeter :”. This question is standard in competitive examination syllabi for Unit And Measurement.

Decibel is the correct answer to “Sound pollution is measured in-”. This question is standard in competitive examination syllabi for Unit And Measurement.

Decibel is the correct answer to “Unit used for measuring the sound is -”. This question is standard in competitive examination syllabi for Unit And Measurement.

energy is the correct answer to “Electron-volt is a unit of”. This question is standard in competitive examination syllabi for Unit And Measurement.

Distance is the correct answer to “Odometer is an instrument which is used in motor vehicle for measuring-”. This question is standard in competitive examination syllabi for Unit And Measurement.

Testing the force of the human voice in speaking is the correct answer to “Phonometer is used to measure which one of the following”. This question is standard in competitive examination syllabi for Unit And Measurement.

Universal constant of gravitation is the correct answer to “Nm 2 kg -2 is SI unit of-”. This question is standard in competitive examination syllabi for Unit And Measurement.

Sphygmomanometer is the correct answer to “The name of the equipment used for measuring blood pressure is”. This question is standard in competitive examination syllabi for Unit And Measurement.

a-4, b-1, c-2, d-3 is the correct answer to “Match the correct. List-I List-II a. Fathometer 1. Atmospheric pressure b. Barometer 2. Atmospheric humidity c. Hygrometer 3. Height d. Altimeter 4. Depth of sea”. This question is standard in competitive examination syllabi for Unit And Measurement.

Weight is the correct answer to “Which of the following is not one of the fundamental quantities in Physics”. This question is standard in competitive examination syllabi for Unit And Measurement.

Work is the correct answer to “Which unit is equal to unit of energy-”. This question is standard in competitive examination syllabi for Unit And Measurement.

Force and Pressure is the correct answer to “In the following which pair has not same unit”. This question is standard in competitive examination syllabi for Unit And Measurement.

Femto is the correct answer to “In terms of SI prefixes 10 -15 is called”. This question is standard in competitive examination syllabi for Unit And Measurement.

Earthquake is the correct answer to “What does a 'seismograph' record”. This question is standard in competitive examination syllabi for Unit And Measurement.

Becquerel is the correct answer to “The SI unit of radioactivity is . . . . . . . .”. This question is standard in competitive examination syllabi for Unit And Measurement.

Force is the correct answer to “Newton is the unit to measure . . . . . . . .”. This question is standard in competitive examination syllabi for Unit And Measurement.

Option "1000Js-1" is the correct answer for this question under Unit And Measurement.

Distance is the correct answer to “Odometer in vehicle measures-”. This question is standard in competitive examination syllabi for Unit And Measurement.

Frequency is the correct answer to “What is measured in hertz”. This question is standard in competitive examination syllabi for Unit And Measurement.

Displacement is the correct answer to “A vector quantity has both magnitude and direction, whereas a scalar quantity has only magnitude and no direction. Which of the following is a vector quantity”. This question is standard in competitive examination syllabi for Unit And Measurement.

Ohm-metre is the correct answer to “The SI unit of electrical resistance of conductor is”. This question is standard in competitive examination syllabi for Unit And Measurement.

Polygraph is the correct answer to “The apparatus used for detecting lie is known as”. This question is standard in competitive examination syllabi for Unit And Measurement.

Lactometer is the correct answer to “Which instrument is used for measuring density of milk”. This question is standard in competitive examination syllabi for Unit And Measurement.

m/s is the correct answer to “The international unit of Speed is-”. This question is standard in competitive examination syllabi for Unit And Measurement.