Answer :
friction always acts to oppose any relative motion between surfaces. if we push on the book with a force of less than 5N , the book wont move, because the frictional force will exactly balance the force we apply. if we push with a 1 N force, a 1 N friction force opposes us.
Friction force is a force that opposes relative motion of two bodies that have contacting surfaces
Yes, the velocity of the book will change as it moves across the surface with friction
Reason:
According to Newton's first law of motion, a body will remain at rest or move with a constant speed in a straight line unless acted on by a force
Friction force, f = Normal reaction, N × Coefficient of friction, μ
A surface with friction has frictional force that opposes the relative motion of an object in surface contact across it
When an object such as a book moves across a surface with friction, the friction force acts on the book having a velocity, opposing the motion of the book, therefore, slowing down the book
Therefore, the velocity of the will change (reduce) as it moves across the surface with friction
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