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

A physical quantity X is related to four measurable quantities a, b, c and d as follows: X = a² b³ c^5/2d^–2. The percentage error in the measurement of a, b, c and d are 1%, 2%, 3% and 4%, respectively. What is the percentage error in quantity X? If the value of X calculated on the basis of the above relation is 2.763, to what value should you round off the result.

A ball is dropped from a building of height 45 m. Simultaneously another ball is thrown up with a speed 40 m/s. Calculate the relative speed of the balls as a function of time.

It is a common observation that rain clouds can be at about a kilometre altitude above the ground.

1. If a rain drop falls from such a height freely under gravity, what will be its speed? Also calculate in km/h. ( g = 10 m/s²)
2. A typical rain drop is about 4mm diameter. Momentum is mass x speed in magnitude. Estimate its momentum when it hits ground.
3. Estimate the time required to flatten the drop.
4. Rate of change of momentum is force. Estimate how much force such a drop would exert on you.
5. Estimate the order of magnitude force on umbrella. Typical lateral separation between two rain drops is 5 cm.

(Assume that umbrella is circular and has a diameter of 1 m and cloth is not pierced through !!)

A man is standing on top of a building 100 m high. He throws two balls vertically, one at t = 0 and other after a time interval (less than 2 seconds). The later ball is thrown at a velocity of half the first. The vertical gap between first and second ball is +15 m at t = 2 s. The gap is found to remain constant. Calculate the velocity with which the balls were thrown and the exact time interval between their throw.

A, B and C are three non-collinear, non co-planar vectors. What can you say about direction of A × (B × C)?

A river is flowing due east with a speed 3 m/s. A swimmer can swim in still water at a speed of 4 m/s (Figure).

1. If swimmer starts swimming due north, what will be his resultant velocity (magnitude and direction)?
2. If he wants to start from point A on south bank and reach opposite point B on north bank, (a) which direction should he swim? (b) what will be his resultant speed?
3. From two different cases as mentioned in (a) and (b) above, in which case will he reach opposite bank in shorter time?

A proton is kept at rest. A positively charged particle is released from rest at a distance d in its field. Consider two experiments; one in which the charged particle is also a proton and in another, a positron. In the same time t, the work done on the two moving charged particles is ______.

A man squatting on the ground gets straight up and stand. The force of reaction of ground on the man during the process is ______.

A cubical block of density ρ is floating on the surface of water. Out of its height L, fraction x is submerged in water. The vessel is in an elevator accelerating upward with acceleration a . What is the fraction immersed?

We would like to make a vessel whose volume does not change with temperature (take a hint from the problem above). We can use brass and iron `(β_(vbrass) = (6 xx 10^(–5))/K and β_(viron) = (3.55 xx 10^(–5))/K)` to create a volume of 100 cc. How do you think you can achieve this.

We would like to make a vessel whose volume does not change with temperature (take a hint from the problem above). We can use brass and iron `(β_(vbrass) = (6 xx 10^(–5))/K and β_(viron) = (3.55 xx 10^(–5))/K)` to create a volume of 100 cc. How do you think you can achieve this.

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 ______.