# Competitive Exams Physics Objective Questions Part 15

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Q-1. A rocket is set for vertical flaring. The exhaust speed is To give an initial upward acceleration of the amount of gas ejected per second to supply the needed thrust will be

a. 137.5 kg/sec

b. 185.5 kg/sec

c. 127.5 kg/sec

d. 187.5 kg/sec

Q-2. A body of mass and velocity collides with a stationary body of mass . After collision both bodies stick to each other. velocity of the bodies after collision will be

a.

b.

c.

d.

Q-3 The earth revolves around the sun with an angular velocity in a circular orbit of radius The force exerted by sun on earth in newton is

a.

b.

c.

d.

Q-4. A bread gives a boy of mass an energy of . If the efficiency is then height can be climbed by him using this energy, is

a.

b.

c.

d.

Q-5. At what height from the earth surface. The acceleration of gravity will be half the value of g at surface?

a.

b.

c.

d.

Q-6. If the gravitational force had varied as instead of The potential energy of a particle at a distance from the centre of the earth would be proportional to

a.

b.

c.

d.

Q-7 A satellite of mass m is circulating around the earth with constant angular velocity. if the radius of the orbit is and mass of the earth is The angular momentum about the centre of the earth momentum about the centre of the earth is

a.

b.

c.

d.

Q-8 A soap bubble has radius r and volume V. if the excess pressure inside the bubble is p. then PV is proportional to

a.

b.

c.

d.

Q-9. If a body of mass falls from a height and its total potential enery is conserved into kinetic potential energy is conserved into kinetic energy, at the point of contact of the body with the surface, then decrease in potential energy of the surface, then decrease in potential energy of the body at the contact is

a. 900 J

b. 600 J

c. 400 J

d. 200 J

Q-10. A particle is projected with at an angle At the highest point, it explodes into three particles of equal masses. One goes vertically upwards with velocity second particle goes vertically downwards. Then the velocity of the third particle will be

a.

b.

c.

d.

Q-11. A cylinder of and radius has moment of inertia is (about its natural axis)

a.

b.

c.

d.

Q-12 If a body starts from rest and travels 120 cm in the 8^{th} second. Then acceleration of the body is

a.

b.

c.

d.

Q-13 A ball is falling in a lake of depth creates a ddecrease in its volume at the bottom. The bilk modulus of the material of the ball will be

a.

c.

d.

Q-14 Waterfalls from a height The rise in temperature of water at bottom if whole of the energy remains in water, will be (specific heat of water )

a.

b.

c.

d.

Q-15 A cylindrical resonance tube, open at both ends, has a fundamental frequency f in air. if half of the length is dipped vertically in water. The fundamental frequency of the air column will be

a.

b.

c.

d.

Answer;

Q-16 A wave frequency has a velocity of . The distance between two nearest points, if the wave is out of phase, will be approximately

a.

b

c.

d.

Q-17 If the momentum of a particle is double, then its de-Broglie wavelength will become

a. Remain unchanged

b. Four times

c. Two times

d. Half times

Q-18. A wave frequency 100 Hz is send along a string towards a fixed end. When this wave travels back, after reflection, a node is formed at a distance of from the fixed end of the string. The speeds of incident (and reflected) waves are

a.

b.

c.

d.

Q-19. A source of sound is travelling with a velocity towards an observer and emits sounds of frequency . If velocity of sounds is , then apparent frequency heard by an observer is

a.

b.

c.

d.

Q-20. What is the dot product of two vectors of magnitude 3 and 5, if angle between them is ?

a.

b.

c.

d.

Q-21. Dimensions of torque are

a.

b.

c.

d.

Q-22. A glass rod of long is clamped at the middle. it is set into the longitudinal vibration. if the emitted sound frequency is , then velocity of sound in glass will be

a.

b.

c.

d.

Q-23. If the critical angle for total internal reflection from a medium to vacuum is Then velocity of light in the medium is

a.

b.

c.

d.

Q-24. The mass of the planet is of the mass of the earth and its radius is half that of the radius of the earth. if a body weighs on the earth, then what will be its weight on planet?

a.

b.

c.

d.

Q-25.16 g of oxygen at is mixed with of nitrogen at the temperature of the mixture will be

a.

b.

c.

d.

Q-26. When there is not heat change from surrounding in a system, then the process is related with

a. isobaric

b. isochoric

c. isothermal

d. adiabatic

Q-27 If the ration of specific heat of a gas at constant pressure to that at constant volume is the change in internal energy of the one mole of a gas when the volume changes from at constant pressure P is

a.

b.

c.

d. PV

Q-28. The original temperature of a black body is The temperature to which that black body must be raised so as to double the total radiant energy, is

a.

b.

c.

d.

Q-29. A particle of mass m and charge q is placed at rest in a uniform electric field E and then released. The kinetic energy field E and then released. The kinetic energy attained by the particle after moving a distance y is

a.

b.

c.

d.

Q-30. Four capacitors each of are connected as shown in diagram the voltmeter reads The charge on each plate of capacitor will be. .

a.

b.

c.

d.

Q-31. electric heater operates on a line, then the rate at which it develops heat in watts will be

a. 1210

b. 810

c. 670

d. 1310

Answer

Q-32. If the magnetic dipole is rotated through angle with respect to the direct of H. Then work done will be

a.

b.

c.

d.

Q-33. If a write of resistance is covered with ice and a voltage of is applied across the wire then rate of melting of ice will be

a.

b.

c.

d. none of these

Q-34. Two identical batteries, each of emf volt and internal resistance by passing a current through it. The maximum power that can be developed across R using these batteries is

a.

b.

c.

d.

Q-35 The angle of minimum deviation for a thin prism with respect to air and when dipped in water will be

a.

b.

c.

d.

Q-36 The velocity of an electronic in the inner most orbit of an atom is

a. highest

b. lowest

c. mean

d. Zero

Q-37. The diameter of the objective lenses of a telescope is and wave length of light is . The limit of resolution of this telescope is

a.

b.

c.

d.

Q-38. Light of wave length falls on a sensitive plate with photoelectric work function of The maximum kinetic energy of the photoelectron emitted will be

a.

b.

c.

d.

Q-39. The mass number of He is 4 and that of sulphur is 32. The radius of sulphur nucleus is larger than that of helium by a factor of

a.

b.

c.

d.

Q-40. A transistor has an it has change in emitter current of 100 milliampere, then the change in the collector current is

a.

b.

c.

d.