Physics MCQ
What is the SI unit of force?
  • Newton (N)
  • Pascal (Pa)
  • Joule (J)
  • Watt (W)
Explanation: It is named after Sir Isaac Newton, a physicist and mathematician who made significant contributions to our understanding of mechanics and the laws of motion.

One Newton is defined as the force required to accelerate a one-kilogram mass by one meter per second squared (1 N = 1 kg·m/s²).

This unit is fundamental in physics, particularly in mechanics, where it is used to quantify the effects of forces on objects.

Forces can cause objects to accelerate, decelerate, change direction, or deform, depending on their magnitude and direction.

Understanding the Newton allows scientists and engineers to calculate and predict the behavior of physical systems under the influence of various forces.

What is Newton's second law of motion?
  • For every action, there is an equal and opposite reaction.
  • The acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass.
  • An object at rest stays at rest, and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.
  • The total momentum of a closed system is constant.
Explanation: This law can be expressed mathematically as: 𝐹 = 𝑚a where:F is the net force acting on the object, 𝑚 is the mass of the object, a is the acceleration produced.

Direct Proportionality to Force: This means that the acceleration ( 𝑎 a) of an object is directly proportional to the force ( 𝐹 F) applied to it.

If you apply a greater force to an object, it will accelerate more. If you apply no force or a balanced force, the object will not accelerate (or will continue moving at a constant velocity if already in motion).

Inverse Proportionality to Mass: This part of the law states that the acceleration of an object is inversely proportional to its mass ( 𝑚 m). In simpler terms, a heavier object requires more force to achieve the same acceleration as a lighter object.

Therefore, acceleration decreases as mass increases, assuming the force remains constant.

Units: In the International System of Units (SI), force is measured in newtons (N), mass in kilograms (kg), and acceleration in meters per second squared (m/s²).

Newton's second law of motion is fundamental in understanding how objects respond to forces and how acceleration relates to force and mass.

 It forms the basis for calculating the dynamics of objects under the influence of external forces.

What is the acceleration due to gravity on Earth?
  • 9.8 m/s²
  • 10 m/s²
  • 9.6 m/s²
  • 8.9 m/s²
Explanation:

Acceleration due to gravity on Earth is approximately 9.8 m/s2.

This value represents the acceleration experienced by objects in free fall near the Earth's surface due to gravity. 

Concept: 1. Definition: Acceleration due to gravity (g) is the acceleration that an object experiences when it falls freely under the influence of gravity. Near the surface of the Earth, this value is approximately constant and is denoted by g.

Concept: 2. Measurement: The standard value of g on Earth is commonly approximated as 9.8 m/s2.

This means that for every second an object falls, its velocity increases by 9.8 m/s.

Concept: 3. Factors Influencing g: The actual value of g can vary slightly depending on factors such as altitude (height above sea level) and latitude (distance from the equator), but these variations are typically minor.

Concept: 4. Units: g is measured in meters per second squared (m/s²), which is the unit of acceleration in the International System of Units (SI).

Understanding the value of g is crucial in various fields of physics, including mechanics, dynamics, and gravitational studies, as it governs the motion of objects falling under the influence of Earth's gravity.

Who formulated the three laws of motion?
  • Albert Einstein
  • Galileo Galilei
  • Isaac Newton
  • Nikola Tesla
Explanation:

Isaac Newton formulated the three laws of motion, which are fundamental principles in classical mechanics. 

 Newton's three laws of motion:

  1. First Law (Law of Inertia): An object at rest will remain at rest, and an object in motion will continue to move at a constant velocity (which could be zero if at rest) unless acted upon by an external force.
  2. Second Law (Law of Acceleration): The acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. Mathematically, F=ma, where F is the force applied, m is the mass of the object, and a is the acceleration produced.
  3. Third Law (Law of Action-Reaction): For every action, there is an equal and opposite reaction. This means that whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first.

Isaac Newton (1642–1727) developed these laws of motion in his work "Mathematical Principles of Natural Philosophy," published in 1687.

These laws laid the foundation for understanding the motion of objects under the influence of forces, and they are still used today to describe the behavior of objects in everyday life, engineering, and astronomy

What is the time taken by the earth to complete one rotation about its axis with regard to a fixed star?
  • Sidereal day
  • Solar day
  • Shake
  • Tropical year
Explanation:

A sidereal day is the time Earth takes to rotate once relative to a fixed star. A solar day is the time Earth takes to rotate relative to the Sun.

A shake, the smallest practical unit of time, equals 10⁻⁸ seconds. A tropical year, unrelated to solar eclipses, is the time for Earth to complete one orbit around the Sun, aligning with the equinoxes.

Water does not fall out of a glass when it is inverted inside a satellite, which is orbiting very close to the earth’s surface. Which of the following is the best reason for this ?
  • A] The earth does not exert any force on the water [B] The earth’s force of attraction on the water is exactly balanced by the force created by the satellites [C] The water and the glass have the same acceleration due to gravity [D] The gravitational attr
  • The earth’s force of attraction on the water is exactly balanced by the force created by the satellites
  • The water and the glass have the same acceleration due to gravity
  • The gravitational attraction between the glass and the water balances the earth’s attraction on the
Explanation: When a glass of water is inverted inside a satellite orbiting close to Earth's surface, the water doesn't fall out because both the glass and the water experience the same gravitational acceleration (g) toward Earth's center. This lack of relative motion between them results in the water staying inside the glass.
Which of the following sounds is produced by earthquakes before the main shock waves?
  • low-frequency infrasound
  • Explanation: Earthquakes emit low-frequency infrasound before the main shock waves, potentially alerting animals. Observations suggest that animals may sense these infrasounds, causing them to exhibit unusual behavior or become disturbed before an earthquake occurs, indicating their ability to detect seismic activity early.