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. A man coming down on a lift leaves a ball from his hand. What will happen to the ball?
[A] Go up
[B] Fall down
[C] Remain stationary with respect to man
[D] Oscillate up and down
Show Answer
Correct Answer: C [Remain stationary with respect to man]
Notes:
If the man and the released ball are experiencing free fall, then the ball would be falling with same acceleration as the boy. Hence relativity says in the man’s view the ball is stationary.
32. Who among the following formulated the Law of Universal Gravitation?
[A] Albert Einstein
[B] Georges Lemaitre
[C] Fred Hoyle
[D] Issac Newton
Show Answer
Correct Answer: D [Issac Newton]
Notes:
Issac Newton formulated the law of univeral gravitation which states that every particle in the universe attracts every other particle and the force of gravitation is inversely proportional to the distance between them. It is also called as inverse square law of gravitation.
33. Which among the following bands of electromagnetic spectrum has least wavelength compared to the remaining?
[A] Radio waves
[B] X rays
[C] Visibel spectrum
[D] Ultraviolet rays
Show Answer
Correct Answer: B [X rays]
Notes:
Descending order of wavelengths of bands of electromagnetic spectrum: Radio waves> Micro waves> Infrared> Visible> Ultraviolet> X rays> Gamma rays. Among the given options, it is X rays with least wavelength.
34. How many half lives does a radio active material need to get reduced to one eighth of the original quantity?
[A] 1
[B] 2
[C] 3
[D] 4
Show Answer
Correct Answer: C [3]
Notes:
Half life period of a material is the time taken to disintegrate half of the atoms of that particular material. After one half life quantity becomes half and after two halflives it becomes quarter of the total and after three halflives it gets half of the quarter i.e. one eighth of the original. (eg: let us take 8 grams, after one half life it becomes 4, after 2 half periods it becomes 2 and after three half lives it becomes 1 which is one eighth of 8 grams).
35. What is it called when two electromagnetic fields interfering with one another and distorting the signals?
[A] Artificial Intelligence
[B] Electronic Intelligence
[C] Electromagnetic Interference
[D] None of the above
Show Answer
Correct Answer: C [Electromagnetic Interference]
Notes:
The phenomenon of two electromagnetic fields interfering with one another and distorting the signals is called electromagnetic interference.
36. According to the Kepler’s law of planetary motion, square of the time period is proportional to__?
[A] semi-major axis
[B] square of the semi-major axis
[C] cube of the semi-major axis
[D] fourth power of the semi-major axis
Show Answer
Correct Answer: C [cube of the semi-major axis]
Notes:
Kepler’s third law of planetary motion states that the square of the time period is proportional to the cube of the semi-major axis. The Ist law states that all planets revolve around the sun in the eliptical orbit while the second law states that all planets sweep equal area, in equal interval of time.
37. What is the SI unit for the average velocity?
[A] m/s
[B] km/s
[C] m/s2
[D] ms
Show Answer
Correct Answer: A [m/s]
Notes:
Velocity is a rate of the change of displacement with respect to time. so SI unit of velocity depend on the SI unit of displacement and time. SI unit of velocity is meter/second.
38. What will be the acceleration (in m/s2) produced in a body of mass 10 kg when a force of 20 N is applied on it?
[A] 200
[B] 4
[C] 2
[D] 100
Show Answer
Correct Answer: C [2]
Notes:
Force is the mass of an object, multiplied by its acceleration. If F is force, m is mass and a is acceleration, it can be expressed as : F = ma According to the question, m = 10 kg, F = 20 N So, a = F/m = 20/10 = 2 m/sec2.
39. Find the acceleration (in m/2) produced in a body of mass 3 kg when a force of 6N is applied on it.
[A] 18
[B] 4
[C] 2
[D] 36
Show Answer
Correct Answer: C [2]
Notes:
Force is the mass of an object, multiplied by its acceleration. If F is force, m is mass and a is acceleration, it can be expressed as: F = ma, or, a = F/m According to the question, m= 3 kg and F = 6 N So, a=6/3= 2 m/sec2.
40. In terms of physics, the movement of a horse lawn carriage is an example of which principle?
[A] Newton third law
[B] Ohm’s law
[C] Archimedes principle
[D] Avogadro’s law
Show Answer
Correct Answer: A [Newton third law]
Notes:
According to Newton’s third law of motion, action force is equal to reaction but acts on two different bodies and in opposite directions. When a horse pushes the ground, the ground reacts and exerts a force on the horse in the forward direction. The force is able to overcome friction force of the cart and it moves.
