ngular momentum of a system to be conserved?","back":"No external torques act on the system.","points":1,"mcqOptions":[{"text":"No external torques act on the system.","correct":true,"explanation":"Angular momentum changes only when a resultant external torque acts. With no external torque, the system’s total angular momentum remains constant, although angular momentum may be transferred internally."},{"text":"No external forces act on the system.","correct":false,"explanation":"External forces need not be absent, because forces directed through the rotation axis produce no torque. The required condition is that no external torques act on the system."},{"text":"No internal torques act on the system.","correct":false,"explanation":"Internal torques can transfer angular momentum between parts of a system but cannot change its total. Conservation requires no external torques to act on the system."},{"text":"No angular acceleration occurs in the system.","correct":false,"explanation":"Parts of a system may undergo angular acceleration while total angular momentum remains conserved, as when moment of inertia changes. The essential condition is the absence of external torques."}]},{"id":"27d215ab-5646-4819-b389-37f19b965a8e","cardType":"basic","front":"How do moment of inertia ($I$) and angular velocity ($\\omega$) change when a diver moves into a \"tuck\" position?","back":"

$I$ decreases (mass is closer to the axis).
$\\omega$ increases (to conserve angular momentum).

","points":2,"mcqOptions":[{"text":"

$I$ decreases (mass is closer to the axis).
$\\omega$ increases (to conserve angular momentum).

","correct":true,"explanation":"Tucking brings the diver’s mass closer to the rotation axis, reducing $I$. Since angular momentum $L=I\\omega$ is conserved, $\\omega$ must increase."},{"text":"

$I$ increases (mass is closer to the axis).
$\\omega$ decreases (to conserve angular momentum).

","correct":false,"explanation":"This reverses both changes. Moving mass closer to the axis decreases moment of inertia, so conservation of $L=I\\omega$ requires angular velocity to increase."},{"text":"

$I$ decreases (mass is closer to the axis).
$\\omega$ decreases (to conserve angular momentum).

","correct":false,"explanation":"The change in $I$ is correct, but reducing both $I$ and $\\omega$ would reduce angular momentum. As $I$ decreases, $\\omega$ must increase to keep $I\\omega$ constant."},{"text":"

$I$ increases (mass is farther from the axis).
$\\omega$ increases (to conserve angular momentum).

","correct":false,"explanation":"A tuck moves mass closer to the axis rather than farther away, so $I$ decreases. Conservation of angular momentum then makes $\\omega$ increase, not because $I$ increases."}]},{"id":"44b081e4-4432-4a8a-b394-a7248a412aa3","cardType":"basic","front":"Why is it incorrect to state that a skater's mass decreases when they pull their arms in?","back":"Mass is constant; only the distribution of mass changes, which alters the moment of inertia.","points":2,"mcqOptions":[{"text":"Mass is constant; only the distribution of mass changes, which alters the moment of inertia.","correct":true,"explanation":"Pulling in the arms does not remove matter from the skater, so total mass stays constant. Moving that mass nearer the axis changes its distribution and reduces moment of inertia."},{"text":"Mass is decreasing; only the angular velocity changes, which alters the moment of inertia.","correct":false,"explanation":"Pulling in the arms does not remove mass, and changing angular velocity does not itself determine moment of inertia. Mass remains constant while

Angular momentum (A-level only)

Angular momentum (A-level only) Flashcards

Angular momentum (A-level only)

Angular momentum (A-level only) Flashcards