Physics

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

(a) The total energy per unit volume

(b) Only the translational part of energy because rotational energy is very small compared to the translational energy

(c) Only the translational part of the energy because during collisions with the wall pressure relates to change in linear momentum

(d) 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

A boy throws a ball in air at 60° to the horizontal along a road with a speed of 10 m/s (36km/h). Another boy sitting in a passing by car observes the ball. Sketch the motion of the ball as observed by the boy in the car, if car has a speed of (18km/h). Give explanation to support your diagram.

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

(a) Will be valid.

(b) Will not be valid since the ions would experience forces other than due to collisions with the walls.

(c) Will not be valid since collisions with walls would not be elastic.

(d) Will not be valid because isotropy is lost.

A boy travelling in an open car moving on a levelled road with constant speed tosses a ball vertically up in the air and catches it back. Sketch the motion of the ball as observed by a boy standing on the footpath. Give explanation to support your diagram.

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

An inflated rubber balloon contains one mole of an ideal gas, has a pressure p, volume V and temperature T. If the temperature rises to 1.1 T, and the volume is increased to 1.05 V, the final pressure will be

(a) 1.1 p

(b) p

(c) Less than p

(d) Between p and 1.1

A football is kicked into the air vertically upwards. What is its (a) acceleration, and (b) velocity at the highest point?

A ball is thrown from a roof top at an angle of 45° above the horizontal. It hits the ground a few seconds later. At what point during its motion, does the ball have

(a) Greatest speed. 

(b) Smallest speed. 

(c) Greatest acceleration? Explain

A vessel of volume V contains a mixture of 1 mole of Hydrogen and 1 mole of Oxygen (both considered as ideal). Let f₁(v)dv, denote the fraction of molecules with speed between v and (v + dv) with f₂(v)dv, similarly for oxygen. Then

(a) f₁(v) + f₂(v) = f(v) obeys the Maxwell's distribution law

(b) f₁(v), f₂(v)will obey the Maxwell's distribution law separately

(c) Neither f₁(v), nor f₂(v) will obey the Maxwell's distribution law

(d) f₂(v) and f1 (v) will be the same

1 mole of H₂ gas is contained in a box of volume V = 1.00 m³ at T = 300K. The gas is heated to a temperature of T = 3000K and the gas gets converted to a gas of hydrogen atoms. The final pressure would be (considering all gases to be ideal)

(a) Same as the pressure initially

(b) 2 times the pressure initially

(c) 10 times the pressure initially

(d) 20 times the pressure initially