Physics MCQs

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Mercury is typically used in barometers because it is denser and more viscous than water, which makes it more effective at measuring changes in atmospheric pressure. It also has High density and low vapor pressure than water. When atmospheric pressure changes, the mercury in the barometer will either rise or fall in the tube, allowing the barometer to accurately measure the pressure. Additionally, mercury has a lower freezing point and a higher boiling point than water, which makes it less likely to freeze or boil at normal temperatures and therefore more reliable for use in a barometer.

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Kelvin is the base unit of temperature (SI unit), having the unit symbol K. The Kelvin temperature scale has an absolute zero (0°K) below which temperatures do not exist. It is the lowest possible temperature. At this temperature there is no motion and no heat. It is equivalent to 0°K, or -273.15° C, or at -460° F.

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This question is related to Antoine equation. Water to get boil, its vapour pressure must reach to its surrounding pressure. In a pressure cooker, it boils at the highest temperature. Elevation of Kochi is 0 m, ooty is 2,486 m, Mount Abu is 1,200 m, New Delhi is 216 m, Shimla is 2,205 m. So comparing all of them, water will boil at lowest temperature at ooty, followed by Shimla, Mount Abu , New Delhi and Kochi. This is because , higher we go lower is the atmospheric pressure and lower is the point where water`s vapour pressure gets equal to the atmospheric pressure.

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Alpha radiation is not used in radiotherapy because it cannot penetrate human skin. Alpha particles are a highly ionizing form of particle radiation with a short range. They can be stopped by a few centimeters of air or by skin. This means that external therapy would be useless because the alpha radiation would not be able to enter the body.  Alpha particles have a very large atomic volume. They are given additional mass by the two neutrons they contain. This facilitates ionization by coulombic interaction or direct collision of the alpha particle with atomic electrons.  Radiation therapy is a treatment that uses ionizing radiation to kill or control the growth of malignant cells. It is often delivered by a linear particle accelerator.

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Thermodynamics is that branch of physics which deals with heat and temperature and their relation to energy (such as mechanical, electrical, or chemical energy) and work. The behaviour of these quantities is governed by the four laws of thermodynamics

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Sidereal day is the time taken by the earth to complete one rotation about its axis w.r.t a fixed star Solar day is the time taken by the earth to complete one rotation about its axis w.r.t the sun. Shake is the smallest practical unit of time 1 shake = 10^-8s Tropical year: The year in which there is a total solar eclipse.

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The unit of impulse is Ns. Impulse = Force(N) x Time(s) Impulse can be defined as the integral of a force, F, over the time interval, t, for which it acts.

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Reynold Number has no units. The Reynolds number is the ratio of inertial forces to viscous forces. It is used for predicting if a flow condition will be laminar or turbulent.

• Unit of Rydberg constant: m^-1
• Unit of Wave number = m^-1
• Unit of Hubble constant = sec^-1

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The physical quantities which have only magnitude and no direction are called as Scalar quantities. Some examples of Scalar quantities: Work, Mass, Temperature, Distance, Speed.

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The Time of Flight, Horizontal Range and the Maximum Height of an object are independent of mass of the object during the projectile motion.