Friction
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Questions and Answers

What is the force of friction that occurs when one body is actually sliding over the surface of another body?

  • Sliding friction (correct)
  • Static friction
  • Rolling friction
  • Kinetic friction

    • What is the coefficient of rolling friction a measure of?

  • The velocity of the rolling object
  • The normal reaction between the surfaces
  • The length of the rolling cylinder or wheel
  • The ratio of the frictional force to the normal reaction (correct)

    • Why are heavy loads often transported on carts with wheels?

  • Because rolling friction is inversely proportional to the normal reaction
  • Because rolling friction is directly proportional to the velocity of the rolling object
  • Because rolling friction is smaller than sliding friction (correct)
  • Because rolling friction is larger than sliding friction

    • What is true about the velocity of the point of contact between the rolling wheel and the surface?

    <p>It remains zero at all times</p> Signup and view all the answers

    What is the relationship between the rolling friction and the radius of the rolling cylinder or wheel?

    <p>Rolling friction is inversely proportional to the radius</p> Signup and view all the answers

    A block of mass m is moving on a rough surface with an initial velocity u. What is the retardation of the block due to friction?

    <p>μg</p> Signup and view all the answers

    A block is moving on an inclined plane with an initial velocity u. What is the net force acting on the block down the plane?

    <p>mg sinθ + μmg cosθ</p> Signup and view all the answers

    A block is stuck to a cart that is accelerating to the right. What is the force exerted by the block on the cart?

    <p>ma</p> Signup and view all the answers

    A block is moving on a rough surface with an initial velocity u. What is the distance travelled by the block before it comes to rest?

    <p>u^2 / (2μg)</p> Signup and view all the answers

    A block is moving on an inclined plane with an initial velocity u. What is the work done by the frictional force on the block as it comes to rest?

    <p>-μmgS</p> Signup and view all the answers

    What is the acceleration of a block sliding up a frictionless inclined plane?

    <p>g sinθ</p> Signup and view all the answers

    When a force F is applied to a block on a rough inclined plane, what is the condition for the block to move up the plane?

    <p>F &gt; μs mg</p> Signup and view all the answers

    What is the work done in moving a block up a rough inclined plane a distance s?

    <p>mgs(sinθ + μcosθ)</p> Signup and view all the answers

    If a force F is applied to the upper body A, and friction is present between A and B, what is the acceleration of the combined system (A and B) when F < F_l?

    <p>F / (m + M)</p> Signup and view all the answers

    What is the force of kinetic friction that opposes the motion of A when F > F_l?

    <p>μk mg</p> Signup and view all the answers

    What is the relationship between the coefficient of static friction and the apparent area of contact?

    <p>It is independent of the apparent area of contact.</p> Signup and view all the answers

    What happens to the force of static friction when the applied force is increased?

    <p>It increases.</p> Signup and view all the answers

    Which type of frictional force arises when one body is actually sliding over the surface of another body?

    <p>Kinetic friction.</p> Signup and view all the answers

    What is the maximum value of static friction called?

    <p>Limiting friction.</p> Signup and view all the answers

    What is the direction of the force of static friction?

    <p>Opposite to the applied force.</p> Signup and view all the answers

    What is the ratio of the force of limiting friction to the normal reaction?

    <p>Coefficient of static friction</p> Signup and view all the answers

    What type of friction occurs when the applied force is increased further and sets the body in motion?

    <p>Kinetic friction</p> Signup and view all the answers

    What is the direction of the force of limiting friction?

    <p>Opposite to the direction of motion</p> Signup and view all the answers

    What is the relation between the coefficient of static friction and the coefficient of kinetic friction?

    <p>μk &lt; μs</p> Signup and view all the answers

    Why do we require more force to start a motion than to maintain it against friction?

    <p>Because of the inertia of rest</p> Signup and view all the answers

    What is the term for the maximum value of static friction?

    <p>Limiting friction</p> Signup and view all the answers

    What type of friction occurs when an object is stationary and is about to move?

    <p>Static friction</p> Signup and view all the answers

    What is the force of friction that occurs when an object is moving?

    <p>Kinetic friction</p> Signup and view all the answers

    What is the graph in Fig. 5.5 representing?

    <p>Applied force and kinetic friction</p> Signup and view all the answers

    What is the purpose of friction in the example of walking?

    <p>To cause motion</p> Signup and view all the answers

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