Kinetic Friction MCQ - Practice Questions & Answers

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A rocket is fired vertically from the earth with an acceleration of 2g, where g is the gravitational acceleration. On an inclined plane inside the rocket, making an angle θ with the horizontal, a point object of mass m is kept. The minimum coefficient of friction ^µ_min between the mass and the inclined surface such that the mass does not move is :

tanθ

2 tanθ

3 tanθ

tan2θ

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The upper half of an inclined plane with inclination $\phi$ is perfectly smooth while the lower half is rough .A body starting from rest at the top will again come to rest at the bottom if the coefficient of friction for the lower half is given by

$2\tan \phi$

$\tan \phi$

$2\sin \phi$

$2\cos \phi$

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Concepts Covered - 1

Kinetic Friction

Kinetic friction occurs when there is relative motion between two bodies which are in contact.
When two bodies slip over each other, the force of friction is called kinetic friction.
It is a constant friction force, i.e, it does not depend upon the speed of relative motion.
The magnitude of the kinetic friction is proportional to the normal force acting between the two bodies.
It is denoted by:-

$f_{K}\;\alpha\ R$