Comprehensive Guide: Important Question
Welcome to our definitive resource for Class 12 physics chapterwise important questions for board exam. As students prepare for the upcoming NEB (National Examination Board) examinations, having access to high-quality, structured study materials is the difference between an average score and achieving distinction. This specific study module focuses deeply on core concepts within Important Question, completely aligned with the latest updated curriculum for the 2082/2083 academic session.
The document provided below contains expertly curated past paper solutions, essential theoretical summaries, and step-by-step problem-solving techniques. By thoroughly reviewing this material, students will develop a stronger foundation in Important Question, allowing them to tackle both conceptual and numerical exam questions with confidence. Examiners frequently test these specific conceptual frameworks, making this a critical area for high-yield revision.
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Check out the important conceptual questions of rotational dynamics.
Rotational dynamics-
A man standing on the turn table extends his hands suddenly. What
happens?
Ans:By extending the hand, the moment of inertia of the system increases and thus angular velocity ω decreases. Now, the turn table will slow down as Iω remains constant in the absence of any external torque. -
Explain why spokes are fitted in the cycle wheel.
Ans:The spokes of cycle wheel increases its moment of inertia. The greater the moment of inertia, the more is the opposition to any change in uniform rotational motion. As a result, cycle runs smoothly and steadily. If the cycle wheels have no spokes, the cycle will be driven jerky and hence be unsafe. -
If the earth is strucked by meteorites, the earth will slow down
slightly. Why?
Ans:When the earth is strucked by meteorites, it remains on the earth and the moment of inertia of the earth increases. As a result, the angular velocity decreases. Hence, the earth slow down slightly. -
Why there are two propellers in a helicopter?
Ans:if there were only one propeller in the helicopter, the helicopter itself would have turned in opposite direction due to conservation of angular momentum. Hence, there are two propellers in helicopter to balance it. -
The angular velocity of the earth around the sun increases when it
comes closer to the sun. Why?
Ans:When the earth come closer to the sun, it's moment of inertia about the axis through the sun decreases. To conserve angular momentum (L = Iω), the angular velocity of the earth increases. -
If a body is rotating, is it necessarily being acted upon by an
external torque?
Ans:Torque is required only for producing angular acceleration. For uniform rotation, no torque is needed. -
Does the angular momentum of a body moving in a circular path
change? Give explanation to your answers.
Ans:No, the angular momentum of a body moving in a circular path doesn't change because the angular momentum always remains conserved if the external torque on it is zero. i.e. L = Iω remain constant where I is moment of inertia and ω is angular speed. -
Why a wrench of longer arm is preferred in comparison to a wrench
of shorter arm?
Ans:A torque is applied to move a wrench, where torque = force × perpendicular distance from the axis of rotation. A smaller force can be applied if the wrench has longer arm for the same torque. We feel easier with small force and therefore, we prefer a wrench of longer arm as compared to that of shorter arm.