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JEE PHYSICS MCQ: WORK-ENERGY-POWER
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An electron and a proton are moving under the influence of mutual forces. In calculating the change in the kinetic energy of the system during motion, one ignores the magnetic force of one on another. This is because,
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Correct option: B
the magnetic forces do no work on each particle.
Option B (the magnetic forces do no work on each particle) is correct because magnetic forces are velocity-dependent and always act perpendicular to the direction of motion, thus doing no work.
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A ball throwing cannon, lifts ball and throws with Speed. If balls are raised upto . then find Input power of cannon if it lifts 8 balls per minute and its efficiency is . Mass of each ball is .
Assertion:When a particle moves in a circle with a uniform speed its acceleration is constant but the velocity changes.
Reason: Angular displacement is not an axial vector. A body of mass thrown vertically upwards attains a maximum height . As what height will its kinetic energy be of its initial value? Assertion: Centripetal force does no work.
Reason: Force and displacement are perpendicular to each other. Statement I: Both stretched and compressed springs possess potential energy.
Statement II: Work done against restoring force is stored as potential energy. A bullet of mass moving at a speed hits a ball of mass kept at rest. A small part having mass breaks from the ball and sticks to the bullet. The remaining ball is found to move at a speed in the direction of the bullet. Find the velocity of the bullet after the collision.
Reason: Angular displacement is not an axial vector. A body of mass thrown vertically upwards attains a maximum height . As what height will its kinetic energy be of its initial value? Assertion: Centripetal force does no work.
Reason: Force and displacement are perpendicular to each other. Statement I: Both stretched and compressed springs possess potential energy.
Statement II: Work done against restoring force is stored as potential energy. A bullet of mass moving at a speed hits a ball of mass kept at rest. A small part having mass breaks from the ball and sticks to the bullet. The remaining ball is found to move at a speed in the direction of the bullet. Find the velocity of the bullet after the collision.