Physics MCQs
Topic Notes: Physics
MCQs and preparation resources for competitive exams, covering important concepts, past papers, and detailed explanations.
Plato
- Biography: Ancient Greek philosopher (427–347 BCE), student of Socrates and teacher of Aristotle, founder of the Academy in Athens.
- Important Ideas:
- Theory of Forms
- Philosopher-King
- Ideal State
71
What is the gravitational force between two spheres, each with a mass of 1000 kg, separated by a distance of 1 meter?
Answer:
6.673 * 10-5
Using Newton's Law of Gravitation, F = G * (m1 * m2) / r^2. Given G = 6.673 * 10^-11 N m^2/kg^2, m1 = m2 = 1000 kg, and r = 1 m. F = 6.673 * 10^-11 * (1000 * 1000) / 1^2 = 6.673 * 10^-5 N. The calculation confirms the result matches the provided option.
72
How would an increase in the Earth's rotational speed affect the acceleration due to gravity at different latitudes?
Answer:
decrease at the equator but remain unchanged at the poles
The effective acceleration due to gravity (g') is given by g' = g - ω²R cos²(λ), where ω is the angular velocity and λ is the latitude. At the equator (λ=0), g' is reduced by the centrifugal term ω²R. If the Earth rotates faster (higher ω), the centrifugal effect increases, further decreasing the effective gravity at the equator. At the poles (λ=90°), the centrifugal term is zero, so gravity remains unchanged.
73
Which of Kepler's laws is derived from the principle of conservation of angular momentum in planetary motion?
Answer:
areas
Kepler's Second Law, the Law of Areas, states that a line segment joining a planet and the Sun sweeps out equal areas during equal intervals of time. This law is a direct consequence of the conservation of angular momentum, which arises because the gravitational force exerted by the Sun on the planet is a central force, exerting no torque.
74
What is the classification for stars that appear as a single point of light to the naked eye but are revealed as two distinct stars when viewed through a telescope?
Answer:
binaries
Binary stars are systems consisting of two stars that orbit around a common center of mass. Due to the vast distances between Earth and these systems, the individual stars often cannot be resolved by the human eye, making them appear as a single star until observed with higher magnification.
75
What is the name of the universal force that causes every object in the universe to exert an attractive force on every other object?
Answer:
force of gravitation
Newton's Law of Universal Gravitation states that every point mass attracts every other point mass by a force acting along the line intersecting both points. This force is proportional to the product of their masses and inversely proportional to the square of the distance between them.
76
Which scientist is credited with the experimental determination of the universal gravitational constant 'G'?
Answer:
Henry Cavendish
While Isaac Newton formulated the Law of Universal Gravitation, he did not measure the value of the constant 'G'. It was Henry Cavendish who, in 1798, successfully measured the gravitational constant using a torsion balance experiment, often referred to as 'weighing the Earth'.
77
The magnitude of the gravitational force acting on an object is equivalent to which of the following expressions?
Answer:
product of mass and acceleration due to the the gravitational force
The gravitational force acting on an object is defined as its weight. By Newton's Second Law, force is equal to the product of mass (m) and acceleration (a). In the context of gravity, the acceleration is the acceleration due to gravity (g), so the force is F = mg.
78
To which objects does the Universal Law of Gravitation apply?
Answer:
Any pair of objects
Newton's Universal Law of Gravitation states that every particle of matter in the universe attracts every other particle with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers. Thus, it applies to any two objects with mass.
79
What is the accepted scientific value for the mass of the Earth?
Answer:
6 × 1024
The mass of the Earth is approximately 5.97 × 10^24 kilograms. In standard physics problems, this value is commonly rounded to 6 × 10^24 kg for simplicity. Therefore, option B represents the standard accepted approximation used in most introductory physics textbooks.
80
At which location on Earth is the weight of an object at its maximum?
Answer:
at the poles
Weight is the product of mass and the acceleration due to gravity (W=mg). Because the Earth is flattened at the poles, the surface is closer to the Earth's center at the poles than at the equator. Consequently, the gravitational force is strongest at the poles, resulting in the maximum weight for any given object.