Suppose your writing desk is tilted a little. A book kept on it starts sliding down. Show the direction of frictional force acting on it.
Solution and Explanation
When a book on a tilted writing desk starts sliding down, the direction of the frictional force will act opposite to the direction of motion. In this case, the frictional force will act upward along the incline of the desk. The purpose of this frictional force is to oppose the sliding motion and prevent the book from accelerating uncontrollably down the tilted surface. It is essentially a kinetic friction force that opposes the relative motion between the book and the desk.
Therefore, friction force acts opposite to the motion of the book.
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Underline the verbs and arrange them in two columns, Past and Earlier past.
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(d) By the time I returned, they had fallen asleep!
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Concepts Used:
Friction
Friction is defined as the resistance offered by the surfaces that are in contact when they move past each other.
Types of Friction
There are four categories of Friction- static friction, sliding friction, rolling friction, and fluid friction.
Sliding Friction
In Sliding Friction, the weight of the sliding object calculates the amount of sliding friction present between the two objects. The sliding friction is supposed to be greater as the pressure exerted by the heavy object on the surface it slides over is comparably more.
Rolling Friction
Friction between a circular object and the surface is called as Rolling Friction. It is required to overcome sliding friction is more than the force required to overcome the rolling friction.
Static Friction
Friction that keeps an object at rest without initiating any relative motion between the body and the surface is termed as Static Friction. For example, a parked car resting on the hill, a hanging towel on the rack. The maximum force of static friction is directly proportional to the normal force.
Fluid Friction
Fluid Friction is the kind of friction that is exerted by the fluid on the object that is moving through a fluid.