21.

A person travelling on a straight line moves with an uniform velocity v₁ for some time and with uniform velocity v₂ for the next equal interval of time. The average velocity for the entire duration is

• ( v₁ + v₂ )

• (v₁ + v₂ ) / 2

• (v₁ + v₂ ) / 3

• (2v₁ + 3v₂ ) / 3 

Rain drops are spherical in shape, because of

• surface tension

• capillarity

• downward motion

• acceleration due to gravity

Volume versus temperature graphs for a given mass of an ideal gas are shown in figure. At two different values of constant pressure, what can be inferred about relation between p₁ and p₂ ?

• p₁ > p₂

• p₁ = p₂

• p₁ < p₂

• data is insufficient

Boyle's law is applicable for an

• adiabatic process

• isothermal process

• isobaric process

• isochoric process

The displacement y of a particle in a medium can be expressed as y =10^-6 sin (l00t + 20x + $\mathrm{\pi }$/ 4) m, where t is in second and x in metre. The speed of the wave is

• 2000 m/s

• 5 m/s

• 20 m/s

• 5$\mathrm{\pi }$ m/s

If the phase difference between two points is 60° on a wave velocity of 360 m/s and frequency 500 Hz, then path difference between the two points is

• 1 cm

• 6 cm

• 12 cm

• 24 cm

In a wave motion y = A sin (kx - ωt), y can represent

• electric field

• magnetic field

• displacement

• pressure

Two particles A and B of masses m and 2m have charges q and 2q respectively. Both  particles moving with velocities v₁ and v₂ respectively in the same direction and enter the same magnetic field B acting normally to their direction of motion. If the two forces F_A and F_B acting on them are in the ratio of 1 : 2, the ratio of their velocities is

• 2 : 1

• 3 : 2

• 2 : 3

• 1 : 1

A narrow beam of protons and deuterons, each having the same momentum, enters a  region of uniform magnetic field directed perpendicular to their direction of momentum. The ratio of the radii of the circular paths described by them is

• 2 : 5

• 3 : 2

• 2 : 3

• 1 : 1

A horizontal overhead power line carries a current of 90 A in east to west direction. The magnitude and direction of the magnetic field due to the current 1.5 m below the line is

• 2.5 x 10^-5 T towards north

• 3 x 10^-5 T towards east

• 1.2 x 10^-5 T towards south

• 1 x 10^-5 T towards west