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The unit of length convenient on the atomic scale is known as an angstrom and is denoted by Å: 1 Å = `10^(–10)` m. The size of a hydrogen atom is about 0.5 Å. What is the total atomic volume in `m^3` of a mole of hydrogen atoms

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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One mole of an ideal gas at standard temperature and pressure occupies 22.4 L (molar volume). What is the ratio of molar volume to the atomic volume of a mole of hydrogen ? (Take the size of hydrogen molecule to be about 1 Å). Why is this ratio so large

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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Explain this common observation clearly : If you look out of the window of a fast moving train, the nearby trees, houses etc. seem to move rapidly in a direction opposite to the train’s motion, but the distant objects (hill tops, the Moon, the stars etc.) seem to be stationary. (In fact, since you are aware that you are moving, these distant objects seem to move with

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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The principle of ‘parallax’ in section 2.3.1 is used in the determination of distances of very distant stars. The baseline AB is the line joining the Earth’s two locations six months apart in its orbit around the Sun. That is, the baseline is about the diameter of the Earth’s orbit `≈ 3 xx 10^(11)`m. However, even the nearest stars are so distant that with such a long baseline, they show parallax only of the order of 1” (second) of arc or so. A parsec is a convenient unit of length on the astronomical scale. It is the distance of an

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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The nearest star to our solar system is 4.29 light years away. How much is this distance in terms of parsecs? How much parallax would this star (named Alpha Centauri) show when viewed from two locations of the Earth six months apart in its orbit around the Sun

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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Just as precise measurements are necessary in science, it is equally important to be able to make rough estimates of quantities using rudimentary ideas and common observations. Think of ways by which you can estimate the following (where an estimate is difficult to obtain, try to get an upper bound on the quantity) : (a) the total mass of rain-bearing clouds over India during the Monsoon (b) the mass of an elephant (c) the wind speed during a storm (d) the number of strands of hair on your head (e) the number of air molecules in your

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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The Sun is a hot plasma (ionized matter) with its inner core at a temperature exceeding `10^7` K, and its outer surface at a temperature of about 6000 K. At these high temperatures, no substance remains in a solid or liquid phase. In what range do you expect the mass density of the Sun to be, in the range of densities of solids and liquids or gases ? Check if your guess is correct from the following data : mass of the Sun = `2.0 ×10^(30)` kg, radius of the Sun = `7.0 × 10^8`

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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When the planet Jupiter is at a distance of 824.7 million kilometers from the Earth, its angular diameter is measured to be 35.72” of arc. Calculate the diameter of

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A man walking briskly in rain with speed v must slant his umbrella forward making an angle θ with the vertical. A student derives the following relation between θ and v : tan θ = v and checks that the relation has a correct limit: as v → 0, θ →0, as expected. (We are assuming there is no strong wind and that the rain falls vertically for a stationary man). Do you think this relation can be correct ? If not, guess the correct

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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It is claimed that two cesium clocks, if allowed to run for 100 years, free from any disturbance, may differ by only about 0.02 s. What does this imply for the accuracy of the standard cesium clock in measuring a time-interval of 1 s

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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Estimate the average mass density of a sodium atom assuming its size to be about 2.5 Å. (Use the known values of Avogadro’s number and the atomic mass of sodium). Compare it with the density of sodium in its crystalline phase : 970 kg `m^(–3)`. Are the two densities of the same order of magnitude ? If so, why

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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The unit of length convenient on the nuclear scale is a fermi : 1 f = `10^(–15)` m. Nuclear sizes obey roughly the following empirical relation : `r=r_oA^(1/3)` where r is the radius of the nucleus, A its mass number, and `r_o` is a constant equal to about, 1.2 f. Show that the rule implies that nuclear mass density is nearly constant for different nuclei. Estimate the mass density of sodium nucleus. Compare it with the average mass density of a sodium atom obtained in Exercise.

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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A LASER is a source of very intense, monochromatic, and unidirectional beam of light. These properties of a laser light can be exploited to measure long distances. The distance of the Moon from the Earth has been already determined very precisely using a laser as a source of light. A laser light beamed at the Moon takes 2.56 s to return after reflection at the Moon’s surface. How much is the radius of the lunar orbit around the Earth

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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A SONAR (sound navigation and ranging) uses ultrasonic waves to detect and locate objects under water. In a submarine equipped with a SONAR the time delay between generation of a probe wave and the reception of its echo after reflection from an enemy submarine is found to be 77.0 s. What is the distance of the enemy submarine? (Speed of sound in water = 1450 m

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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The farthest objects in our Universe discovered by modern astronomers are so distant that light emitted by them takes billions of years to reach the Earth. These objects (known as quasars) have many puzzling features, which have not yet been satisfactorily explained. What is the distance in km of a quasar from which light takes 3.0 billion years to reach us

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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It is a well known fact that during a total solar eclipse the disk of the moon almost completely covers the disk of the Sun. From this fact and from the information you can gather from examples 2.3 and 2.4, determine the approximate diameter of the

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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A great physicist of this century (P.A.M. Dirac) loved playing with numerical values of Fundamental constants of nature. This led him to an interesting observation. Dirac found that from the basic constants of atomic physics (c, e, mass of electron, mass of proton) and the gravitational constant G, he could arrive at a number with the dimension of time. Further, it was a very large number, its magnitude being close to the present estimate on the age of the universe (~15 billion years). From the table of fundamental constants in this book, try to see if you too can construct

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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A book with many printing errors contains four different formulas for the displacement y of a particle undergoing a certain periodic motion : (a) y = a sin 2π t/T (b) y = a sin vt (c) y = (a/T) sin t/a (d) y`(asqrt2)`(sin 2πt/T + cos 2πt/T ) (a = maximum displacement of the particle, v = speed of the particle. T = time-period of motion). Rule out the wrong formulas on dimensional

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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If `x = at + bt^2` where x is in meters and t is in seconds. What are the units of a and

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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Fill ups.(i) 3.0m/`s^2 `= ________ km/`hr^2`(ii) `6.67 10^(-11)Nm^2`/`kg^2 = `_________`g^(-1)cm^3s

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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