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 (B)</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 (B)</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 (A)</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 (A)</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 (D)</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) (C)</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 (A)</p> Signup and view all the answers

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

<p>g sinθ (B)</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 (C)</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) (D)</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) (C)</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 (B)</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. (D)</p> Signup and view all the answers

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

<p>It increases. (A)</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. (D)</p> Signup and view all the answers

What is the maximum value of static friction called?

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

What is the direction of the force of static friction?

<p>Opposite to the applied force. (D)</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 (D)</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 (A)</p> Signup and view all the answers

What is the direction of the force of limiting friction?

<p>Opposite to the direction of motion (A)</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 (C)</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 (D)</p> Signup and view all the answers

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

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

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

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

What is the graph in Fig. 5.5 representing?

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

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

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

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