Physics (Railway) Part-I

Total Questions: 50

21. Which of the following physicists explained the existence of Buoyant force? [RRB ALP & Technician Exam, 13.08.2018 Shift-I]

Correct Answer: (1) Archimedes
Solution:Buoyancy (also known as the buoyant force) is the force exerted on an object that is wholly or partly immersed in a fluid. It was first explained by Archimedes who stated that the upward buoyant force that is exerted on a body immersed in a fluid, whether fully or partially submerged. is equal to the weight of the fluid that the body displaces and acts in the upward direction at the centre of mass of the displaced fluid.

22. Which of the following is a surface phenomenon? [RRB ALP & Technician Exam, 13.08.2018 Shift-I]

Correct Answer: (3) Evaporation
Solution:Surface phenomenon is the phenomenon where only surface of any substance or object is involved in the process.In evaporation, the molecules of the liquid present on the surface of the liquid leave the liquid state and change into vapour state without affecting the molecules present in the bulk of the liquid. Thus, evaporation is a surface phenomenon. If the surface area is increased, the rate of evaporation increases.

23. Kinetic energy of an object increases in proportion to? [RRB ALP & Technician Exam, 13.08.2018 Shift-I]

Correct Answer: (4) Speed
Solution:Kinetic energy is energy possessed by an object in motion. It is directly proportional to the mass of the object and to the square of its

velocity: K.E. = 1/2 mv², where

m is mass and u is velocity of the object. That means that for a two fold increase in speed, the kinetic energy will increase by a factor of four. For a threefold increase in speed, the kinetic energy will increase by a factor of nine.

24. If the power of a corrective lens is +2. 0D, then it is a: [RRB ALP & Technician Exam, 13.08.2018 Shift-I]

Correct Answer: (1) convex lens
Solution:The power of a lens is defined as the ability of the lens to converge or diverge a beam of light falling on it. The power of a convex lens is positive as a convex lens has a positive focal length, while the power of a concave lens is negative as concave lens has a negative focal length.

25. Insulators have resistivity of the order of: [RRB ALP & Technician Exam, 13.08.2018 Shift-I]

Correct Answer: (4) 10¹² Ωm to 10¹⁷ Ωm
Solution:Resistivity is a measure of the resistance to electrical conduction for a given size of material. Its opposite is electrical conductivity. Electrical insulators have resistivities in the range 10¹² to 10²⁰ ohmmetres. The resistivity of an insulator varies greatly with the purity and surface condition of the material, time of application of the voltage, and in some cases with the magnitude of the applied stress.

26. Which of the following devices helps to maintain a potential difference across a conductor? [RRB ALP & Technician Exam, 13.08.2018 Shift-I]

Correct Answer: (3) A cell or battery
Solution:Potential difference is the amount of work energy required to move an electric charge from one point to another. A source of electricity such as cell, battery, power supply, etc. helps to maintain a potential difference across a conductor.

27. The unit of power used in industry is: [RRB ALP & Technician Exam, 13.08.2018 Shift-III]

Correct Answer: (2) Horse power
Solution:Horsepower (hp) is a unit of measurement of power (the rate at which work is done). The term horsepower was invented by the engineer James Watt.

28. Mechanical energy is the sum of: [RRB ALP & Technician Exam, 13.08.2018 Shift-III]

Correct Answer: (2) kinetic energy + potential energy
Solution:In physical sciences, mechanical energy is the sum of potential energy and kinetic energy. It is the energy associated with the motion and position of an object.

29. Which of the following is not a voluntary action? [RRB ALP & Technician Exam, 13.08.2018 Shift-III]

Correct Answer: (3) Beating of heart
Solution:Beating of heart is not a voluntary action.

30. In Force equation, F is equal to: [RRB ALP & Technician Exam, 13.08.2018 Shift-III]

Correct Answer: (4) ma
Solution:Newton's second law of motion describes the relationship between an object's mass and the amount of force needed to accelerate it. Newton's second law is often stated as F=ma, which means the force (F) acting on an object is equal to the mass (m) of an object times its acceleration (a).