MCQ Questions for Class 12 Hindi with Answers

Explanation: This question asks you to identify an incorrect statement about the four basic forces that govern interactions in nature. These forces differ significantly in strength, range, and the types of particles they influence. Gravitational force acts between masses and is always attractive but extremely weak compared to the others. Electromagnetic force operates between charged particles and can be either attractive or repulsive. The weak nuclear force is responsible for certain types of particle transformations, especially those seen in radioactive decay. The strong nuclear force is the most powerful of all and acts over very short distances, holding protons and neutrons tightly together within the nucleus despite the repulsion between positively charged protons. To evaluate the statements, compare each force based on its known characteristics such as strength, range, and function. Any mismatch between these properties and the description provided would indicate an incorrect statement. For instance, confusing the relative strengths or roles of these forces can lead to incorrect conclusions. Understanding their hierarchy and behavior helps in identifying inconsistencies. In summary, recognizing the defining features of each fundamental force allows you to carefully assess which statement does not align with established physical principles.

Explanation: This question explores how a person’s apparent weight changes inside a moving lift depending on its motion. Apparent weight is the force exerted by the floor on the person, which can vary from the actual weight due to acceleration. When the lift is stationary or moving at a constant velocity, there is no change in apparent weight because acceleration is zero. However, when the lift accelerates, additional forces come into play. If the lift accelerates upward, the floor must push the person upward more strongly to counteract both gravity and the upward acceleration, increasing the normal reaction force. Conversely, if the lift accelerates downward, the support force from the floor decreases, making the person feel lighter. This effect can be explained using Newton’s second law, where NET force depends on both Mass and acceleration. The sensation of heaviness or lightness is directly related to the magnitude of this support force. By analyzing the direction and nature of acceleration, one can determine when the apparent weight increases. In essence, changes in motion—not just movement itself but acceleration—are responsible for variations in how heavy a person feels inside the lift.

Explanation: This question focuses on why a moving object eventually stops even after being given an initial push. According to basic mechanics, an object in motion would continue moving indefinitely unless acted upon by an external force. In real-life situations, surfaces are not perfectly smooth, and interactions between the ball and the ground introduce resistive forces. These include friction between the ball and the surface and air resistance opposing motion. Friction acts in the direction opposite to the motion of the ball, gradually reducing its speed over time. As the ball slows down, its kinetic energy is dissipated, mainly as Heat due to surface interactions. Eventually, the resistive forces reduce the velocity to zero, bringing the ball to rest. The key idea is that unbalanced forces are responsible for changes in motion, including stopping. Without such opposing forces, the ball would continue rolling. Thus, analyzing the presence and direction of forces helps explain why motion does not persist forever in everyday conditions. In summary, the gradual loss of motion occurs due to forces acting against the direction of movement, leading to eventual rest.

Explanation: This question examines the factors that influence the time taken by a pendulum to complete one full Oscillation. A simple pendulum consists of a small Mass suspended by a string and swinging under the influence of gravity. Its motion is Periodic, and the time period depends on certain physical parameters. From experimental observations and theoretical derivation, the time period is expressed using a formula that includes the length of the pendulum and the acceleration due to gravity. Notably, the Mass of the bob does not affect the time period, nor do minor variations in temperature under normal conditions. The dependence arises because a longer pendulum takes more time to complete a swing, while a shorter one oscillates faster. The motion is governed by restoring forces that depend on displacement and gravitational acceleration. By comparing different influencing factors, it becomes clear which parameter has the most significant effect. In summary, identifying the variables present in the governing relation helps determine the main factor affecting the time period of a simple pendulum.

Explanation: This question deals with the motion of a satellite that appears to remain fixed relative to a point on Earth while actually moving in orbit. A geosynchronous satellite travels around Earth with a period equal to Earth’s rotation. For circular motion, a centripetal force is required to keep the satellite in orbit, and this is provided by gravitational attraction. At the same time, from the satellite’s rotating frame of reference, an outward centrifugal effect is observed. This effect arises due to the satellite’s motion along a curved path at a constant speed. The balance between inward gravitational pull and outward centrifugal tendency ensures stable motion. The origin of this outward effect is not due to engines or external pushes but due to the satellite’s inertia while moving in a circular path. Understanding circular motion helps clarify that the apparent outward force is a result of continuous motion rather than an independent force source. In summary, the sustained orbital motion depends on the interplay between gravitational attraction and the centrifugal effect generated by circular motion.

Explanation: This question explores the fundamental reason why satellites stay in orbit instead of moving away or falling directly to Earth. Circular motion requires a continuous inward force to change the direction of velocity, even if speed remains constant. In the case of a satellite, Earth’s gravitational pull provides this necessary inward force. Without this force, the satellite would travel in a straight line due to inertia. The motion can be understood as a constant “fall” toward Earth, where the satellite keeps missing the surface because of its high tangential velocity. This balance between forward motion and inward pull results in a stable orbit. The concept is closely tied to centripetal force, which always acts toward the center of the circular path. By analyzing the forces acting on the satellite, one can determine the primary reason for its continued revolution. In summary, the presence of an inward-directed force that constantly alters the direction of motion allows the satellite to remain in orbit around Earth.