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
1
Evaluate the following statements regarding Newton's Third Law of Motion: Assertion (A) states the law applies only to bodies in motion, while Reason (R) states it applies to all types of forces.
Answer:
A is false, but R is true
Newton's Third Law states that for every action, there is an equal and opposite reaction. This law applies to all forces, whether the objects are at rest or in motion. Therefore, Assertion (A) is false because the law is not restricted to moving bodies. Reason (R) is true as the law is universal for all fundamental forces, including gravitational and electromagnetic interactions.
2
A body of mass 100 kg increases its speed from 5 m/s to 15 m/s over a duration of 5 seconds under uniform acceleration. Calculate the force exerted on the body.
Answer:
200 N
First, calculate acceleration: a = (v_final - v_initial) / time = (15 - 5) / 5 = 10 / 5 = 2 m/s². Then, apply Newton's Second Law: Force = mass * acceleration = 100 kg * 2 m/s² = 200 N. The unit of force is the Newton (N).
3
According to Newton's Second Law of Motion, what is the mathematical expression for force (F) in terms of mass (m) and acceleration (a)?
Answer:
ma
Newton's Second Law of Motion states that the force acting on an object is equal to the product of its mass and its acceleration, expressed by the formula F = ma. This law describes how the velocity of an object changes when it is subjected to an external force.
4
Which statement accurately describes Newton's Third Law of Motion?
Answer:
The force is applied on different body in opposite direction
Newton's Third Law states that for every action, there is an equal and opposite reaction. Crucially, these forces act on two different bodies. If body A exerts a force on body B, body B simultaneously exerts an equal and opposite force on body A. Because the forces act on different objects, they do not cancel each other out in terms of the motion of a single body.
5
Comparing two objects of identical mass, one moving and one at rest, which possesses greater inertia?
Answer:
Both have same inertia because inertia depends upon mass only
Inertia is defined as the inherent property of a body to resist changes in its state of motion or rest. According to classical mechanics, inertia is directly proportional to the mass of the object. Since both bodies have the same mass, they possess the same amount of inertia, regardless of their current velocity or state of motion.
6
A constant force is applied to an 8 kg object for 2 seconds, increasing its velocity from 4 m/s to 9 m/s. What is the magnitude of this force?
Answer:
20 N
According to Newton's Second Law, force is the rate of change of momentum: F = m * (v_final - v_initial) / t. Substituting the values: F = 8 kg * (9 m/s - 4 m/s) / 2 s = 8 * 5 / 2 = 40 / 2 = 20 Newtons.
7
Calculate the total force applied to an object with a mass of 2 kg that is moving with an acceleration of 4 m/s².
Answer:
8.0 N
According to Newton's Second Law of Motion, the net force acting on an object is equal to the product of its mass and acceleration (F = ma). Given mass m = 2 kg and acceleration a = 4 m/s², the force F = 2 kg * 4 m/s² = 8.0 N.
8
Which physical principle explains the propulsion of a rocket?
Answer:
Newton's Third Law
A rocket operates based on Newton's Third Law of Motion, which states that for every action, there is an equal and opposite reaction. As the rocket engine expels exhaust gases at high velocity in one direction (action), the gases exert an equal and opposite force on the rocket, propelling it forward (reaction).
9
Which physical principle governs the operation of a washing machine during its spin cycle?
Answer:
Centrifugation
A washing machine utilizes centrifugal force during the high-speed spin cycle. As the drum rotates rapidly, the clothes are forced against the perforated walls. Water and dissolved dirt are pushed outward through the perforations due to inertia, effectively separating the liquid from the solid fabric. This application of circular motion is a classic example of centrifugation.
10
How is Newton's Second Law of Motion formally defined?
Answer:
The rate of change of momentum of an object is proportional to the net force applied to the object in the direction of net force
Newton's Second Law states that the rate of change of momentum of a body is directly proportional to the applied unbalanced force and takes place in the direction of the force. Mathematically, F = dp/dt, which simplifies to F = ma for constant mass systems.