Physics (Part-II) (Railway)

Total Questions: 50

31. The centre of the reflecting surface of a spherical mirror is a point called the ________. [RRB ALP & Technician Exam, 31.08.2018 Shift-I]

(1) pole
(2) aperture
(3) radius
(4) focus

Correct Answer: (1) pole

Solution:The center of the reflecting surface of a spherical mirror is called as the pole of the mirror. In addition to this, the straight line passes through this center of the reflecting surface in a spherical mirror that is termed as a Principal axis.

32. What is the value of acceleration due to gravity on the surface of the earth? [RRB ALP & Technician Exam, 31.08.2018 Shift-I]

(1) 10.8 m/s²
(2) 9.8 cm/s²
(3) 9.6 cm/s²
(4) 9.8 m/s²

Correct Answer: (4) 9.8 m/s²

Solution:Acceleration of gravity is dependent upon the mass of the earth and the distance that an object is from the center of the earth. The acceleration of gravity on the surface of the earth at sea level is 9.8 m/s². However, it changes with the change in latitude or altitude or depth.

33. In a longitudinal wave, the distance between two consecutive compressions or two consecutive rarefactions is called: [RRB ALP & Technician Exam, 31.08.2018 Shift-III]

(1) Matter
(2) Wavelength
(3) Magnitude
(4) Energy

Correct Answer: (2) Wavelength

Solution:Wavelength is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings and is a characteristics of traveling waves and standing waves, as well as other spatialwave patterns. Longitudinal waves have compressions and rarefactions.

34. As a sailor jumps in the forward direction, the boat moves backwards. This example illustrates Newton's: [RRB ALP & Technician Exam, 31.08.2018 Shift-III]

(1) Second Law of Motion
(2) First and Second Law of Motion
(3) Third Law of Motion
(4) First Law of Motion

Correct Answer: (3) Third Law of Motion

Solution:Newton's third law states that for every action, there is an equal and opposite reaction. When the sailor jumps down the boat, he applies pressure on the boat with the feet. The greater the pressure is the boat moves backward with equal force but in opposite direction. Pressure applied is the action whereas the movement of boat is the reaction.

35. Which of the following statements is/are INCORRECT? [RRB ALP & Technician Exam, 31.08.2018 Shift-III]

A. The value of G on the moon is equal to that on the earth.

B. 26.68 * 10-¹¹ N is the force of gravitation between two points masses of 2 kg and 2 kg kept 1 m apart.

C. Newton's law of gravitation is valid in the laboratory only.

D. Force is inversely proportional to the square of the distance between two bodies.

(1) B, C and D
(2) only C and D
(3) Only C
(4) Only A

Correct Answer: (3) Only C

Solution:Newton's law of universal gravitation states that every particle attracts every other particle in the universe with a force which is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers.

36. Which of the following can do more work? [RRB ALP & Technician Exam, 31.08.2018 Shift-III]

(1) A rotating wheel
(2) A moving bullet
(3) A speeding stone
(4) A raised hammer

Correct Answer: (2) A moving bullet

Solution:A moving object has momentum, which is the product of its mass and its velocity. In physics, a force is said to do work if, when acting, there is a displacement of the point of application in the direction of the force. Thus, work done by a force acting on an object is equal to the magnitude of the force multiplied by the distance moved in the direction of the force. A moving bullet can do more work because of its Kinetic energy.

37. The speed of the light is maximum in: [RRB ALP & Technician Exam, 31.08.2018 Shift-III]

(1) Air
(2) Vacuum
(3) Water
(4) Glass

Correct Answer: (2) Vacuum

Solution:Light is an electromagnetic wave. An electromagnetic wave can travel through anything - be it air, a solid material or vacuum. It does not need a medium to propagate or travel from one place to another. The speed of light is maximum in vacuum.

The speed of light in vacuum, commonly denoted by C. is a universal physical constant important in many areas of physics. Its exact value is 299,792,458 metres per second (approximately 300,000 km/s).

38. A potential difference of 50 V is applied across a resistor of resistance 10000 for 10 secs. What will be the amount of heat generated in the circuit? [RRB RPF/RPSF SI Exam, 04.09.2018 Shift-I]

(1) 250 J
(2) 25 J
(3) 500 J
(4) 50 J

Correct Answer: (2) 25 J

Solution:The heat generated in a circuit is given by H = I²Rt joule where I is current, R is resistance and t is time.

From Ohm's Law, we know V [Potential Difference) = I (Current) x R (Resistance)

So according to the question,

I = V/R = 50/1000 = 1/20 A

So Heat generated in the circuit = (1/20)² x 1000 x 10

= 10000/400 = 25 Joules

39. In a parallel combination, the potential difference across each resistance is _, which is ___ the voltage of the battery applied. [RRB RPF/RPSF SI Exam, 04.09.2018 Shift-I]

(1) unequal, the same as
(2) the same, equal to
(3) twice, the same as
(4) half, the same as

Correct Answer: (2) the same, equal to

Solution:Parallel circuits are by definition circuits that have common start and end points. The starting point of all the parallel circuits being the same, the potential at their start point is also same. Similarly the potential of end point of all the parallel circuit is also same. The potential of start and end point of all parallel circuits being same, their potential difference is also same. Each resistor in parallel has the same voltage equal to the source applied to it (voltage is constant in a parallel circuit).

40. Fill in the blank with the most appropriate option. [RRB RPF/RPSF SI Exam, 04.09.2018 Shift-I]

Very fine particles mainly scatter_________ light in the atmosphere.

(1) red
(2) blue
(3) white
(4) orange

Correct Answer: (2) blue

Solution:Light is scattered when it falls on various objects. The colour of the scattered light depends on the size of the scattering particle. Very fine particles scatter mainly blue light while particles of larger size scatter light of longer wavelengths i.e. red colour. If the size of the particle is very large, the scattered light may appear white.

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