JEE Main Physics question
Which of the following statements are incorrect? (i) If there were no friction, work need to be done to move a body up an inclined plane is zero. (ii) If there were no friction, moving vehicles could not be stopped even by locking the brakes. (iii) As the angle of inclination is increased, the normal reaction on the body placed on it increases. (iv) A duster weighing 0.5 kg is pressed against a vertical board with a force of 11 N. If the coefficient of friction is 0.5, the work done in rubbing it upward through a distance of 10 cm is 0.55 J. [UP SEE 2008]
Solution
(i) is incorrect — even with no friction, work must still be done against gravity to raise the body up the incline. (ii) is incorrect — friction (not inertia) is what allows brakes to actually stop a vehicle; without friction, locked wheels would
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