Science (English Medium) कक्षा ११ - CBSE Question Bank Solutions for Physics

A cubic vessel (with faces horizontal + vertical) contains an ideal gas at NTP. The vessel is being carried by a rocket which is moving at a speed of 500 ms^–1 in vertical direction. The pressure of the gas inside the vessel as observed by us on the ground ______.

1 mole of an ideal gas is contained in a cubical volume V, ABCDEFGH at 300 K (Figure). One face of the cube (EFGH) is made up of a material which totally absorbs any gas molecule incident on it. At any given time ______.

ABCDEFGH is a hollow cube made of an insulator (Figure). Face ABCD has positive charge on it. Inside the cube, we have ionized hydrogen. The usual kinetic theory expression for pressure ______.

1. will be valid.
2. will not be valid since the ions would experience forces other than due to collisions with the walls.
3. will not be valid since collisions with walls would not be elastic.
4. will not be valid because isotropy is lost.

Diatomic molecules like hydrogen have energies due to both translational as well as rotational motion. From the equation in kinetic theory `pV = 2/3` E, E is ______.

1. the total energy per unit volume.
2. only the translational part of energy because rotational energy is very small compared to the translational energy.
3. only the translational part of the energy because during collisions with the wall pressure relates to change in linear momentum.
4. the translational part of the energy because rotational energies of molecules can be of either sign and its average over all the molecules is zero.

In a diatomic molecule, the rotational energy at a given temperature ______.

1. obeys Maxwell’s distribution.
2. have the same value for all molecules.
3. equals the translational kinetic energy for each molecule.
4. is (2/3)rd the translational kinetic energy for each molecule.

When an ideal gas is compressed adiabatically, its temperature rises: the molecules on the average have more kinetic energy than before. The kinetic energy increases ______.

1. because of collisions with moving parts of the wall only.
2. because of collisions with the entire wall.
3. because the molecules gets accelerated in their motion inside the volume.
4. because of redistribution of energy amongst the molecules.

The container shown in figure has two chambers, separated by a partition, of volumes V₁ = 2.0 litre and V₂ = 3.0 litre. The chambers contain µ₁ = 4.0 and µ₂ = 5.0 moles of a gas at pressures p₁ = 1.00 atm and p₂ = 2.00 atm. Calculate the pressure after the partition is removed and the mixture attains equilibrium.

We have 0.5 g of hydrogen gas in a cubic chamber of size 3 cm kept at NTP. The gas in the chamber is compressed keeping the temperature constant till a final pressure of 100 atm. Is one justified in assuming the ideal gas law, in the final state?

(Hydrogen molecules can be consider as spheres of radius 1 Å).

When a mass m is connected individually to two springs S₁ and S₂, the oscillation frequencies are ν₁ and ν₂. If the same mass is attached to the two springs as shown in figure, the oscillation frequency would be ______.

One end of a V-tube containing mercury is connected to a suction pump and the other end to atmosphere. The two arms of the tube are inclined to horizontal at an angle of 45° each. A small pressure difference is created between two columns when the suction pump is removed. Will the column of mercury in V-tube execute simple harmonic motion? Neglect capillary and viscous forces. Find the time period of oscillation.

Show that the area of the triangle contained between the vectors a and b is one half of the magnitude of a × b.

The relative density of lead is 11.3. Its density is ______ g cm^–3or ______ kg m^–3.

A student measures the thickness of a human hair by looking at it through a microscope of magnification 100. He makes 20 observations and finds that the average width of the hair in the field of view of the microscope is 3.5 mm. What is the estimate on the thickness of hair?

You are given a thread and a metre scale. How will you estimate the diameter of the thread?

A screw gauge has a pitch of 1.0 mm and 200 divisions on the circular scale. Do you think it is possible to increase the accuracy of the screw gauge arbitrarily by increasing the number of divisions on the circular scale?

The mean diameter of a thin brass rod is to be measured by vernier callipers. Why is a set of 100 measurements of the diameter expected to yield a more reliable estimate than a set of 5 measurements only?

The photograph of a house occupies an area of 1.75 cm²on a 35 mm slide. The slide is projected on to a screen, and the area of the house on the screen is 1.55 m². What is the linear magnification of the projector-screen arrangement?

The length, breadth, and thickness of a rectangular sheet of metal are 4.234 m, 1.005 m, and 2.01 cm respectively. Give the area and volume of the sheet to correct significant figures.

The mass of a box measured by a grocer’s balance is 2.300 kg. Two gold pieces of masses 20.15 g and 20.17 g are added to the box. What is

1. What is the total mass of the box?
2. What is the difference in the masses of the pieces to correct significant figures?

Precise measurements of physical quantities are a need of science. For example, to ascertain the speed of an aircraft, one must have an accurate method to find its positions at closely separated instants of time. This was the actual motivation behind the discovery of radar in World War II. Think of different examples in modern science where precise measurements of length, time, mass etc. are needed. Also, wherever you can, give a quantitative idea of the precision needed.