Physics MCQs
Physics Objective (Multiple Choice) General Knowledge & General Science Questions & Answers for SSC-CGL, UPPSC, NDA, CDS and all one day examinations of India.
31. What is the charge of X rays?
[A] Positive
[B] Negative
[C] No charge
[D] Charge varies
Show Answer
Correct Answer: C [No charge]
Notes:
X rays are part of electromagnetic spectrum which does not contain any charge i.e. it is neutral.
32. Which term is used to define the ratio of speed of the object to the speed of sound in that particular medium?
[A] Avogadro number
[B] Tach number
[C] Mach number
[D] Bernoulis number
Show Answer
Correct Answer: C [Mach number]
Notes:
Mach number is defined as the ratio of speed of the object to the speed of sound in that particlar medium. Speed of the aeroplanes and airforce jet planes are expressed on mach numbers.
33. Match the following items of column (A) with column (B):
Column A
- I. Electron
- II. Proton
- III. Neutron
Column B
- Rutherford
- Thomson
- Chadwick
[A] I – 3, II – 1, III – 2
[B] I – 2, II – 1, III – 3
[C] I – 2, II – 3, III – 1
[D] I – 1, II – 2, III – 3
Show Answer
Correct Answer: B [I – 2, II – 1, III – 3]
Notes:- Electron: discovered by J.J. Thomson in 1897 when he was studying the properties of cathode ray;
- Proton: discovered by Ernest Rutherford, in his famous gold foil experiment;
- Neutron: discovered by Sir James Chadwick, an English physicist, in 1932.
34. A micron is equal to__:
[A] 0.1 mm
[B] 0.01 mm
[C] 0.001 mm
[D] 0.0001 mm
Show Answer
Correct Answer: C [0.001 mm]
Notes:
1 micron = 0.001 millimeters or 10 .6 m. A micrometre (micron) is one-millionth of a metre (or one-thousandth of a millimetre, 0.001 mm). Its unit symbol in the International System of Units (SI) is ƒÊm. It is a common unit of measurement for wavelengths of infrared radiation as well as sizes of cells and bacteria.
35. The dimensional formula for universal gravitational constant is
[A] M-1 L3 T-2
[B] M2 L2 T-2
[C] M-1 L-1 T-2
[D] M-1 L3 T-2
Show Answer
Correct Answer: D [M-1 L3 T-2]
Notes:
G = [M1 L1 T-2] × [M0 L1 T0]2 × [M1 L0 T0]-1 × [M1 L0 T0]-1 = M-1 L3 T-2. So, dimensional formula for universal gravitational constant is [M-1 L3 T-2].
36. What would be the angle of projection if horizontal range of a projectile is four times its maximum height?
[A] 30°
[B] 45°
[C] 60°
[D] 75°
Show Answer
Correct Answer: B [45°]
Notes:
37. Which of the following is the unit of Astronomical Distance ?
[A] metre/sec.
[B] Sec.
[C] Para/sec.
[D] Parsec
Show Answer
Correct Answer: D [Parsec]
Notes:
A parsec is a unit of length used to measure large distances between objects outside our Solar System. One parsec is the distance equal to about 3.26 lightyears in length.
38. Which of the following is not a vector quantity?
[A] Momentum
[B] Displacement
[C] Torque
[D] Speed
Show Answer
Correct Answer: D [Speed]
Notes:
Speed is a scalar quantity that measures the rate at which an object changes its position. It refers only to how fast an object is moving, without any information about the direction. On the other hand, momentum, displacement, and torque are all vector quantities. They require both a magnitude and direction to fully describe them. Therefore, out of the options, speed is the one that is not a vector quantity.
39. If the acceleration due to gravity on the surface of earth is g, then the acceleration due to gravity on the surface of a planet whose mass is same as that of earth and radius is twice as that of earth is__:
[A] g/4
[B] g/2
[C] 4g
[D] 2g
Show Answer
Correct Answer: A [g/4]
Notes:
Acceleration due to gravity is given by the formula : g = GM/r2 According to the question, mass of the second planet is same as that of earth and radius is twice So, using the formula of g, we get the acceleration due to gravity of the second planet as g/4.
40. Calculate the pressure (in Pa) if a thrust of 1000 N is applied to an area of 5 m2.
[A] 200
[B] 50
[C] 100
[D] 25
Show Answer
Correct Answer: A [200]
Notes:
Thrust is defined as Force exerted by an object perpendicular to the surface; while, Pressure is simply Force exerted by any object per unit area. In other words, Pressure = Thrust/Area So, according to the question, Pressure = 1000/5 = 200 Pa
