Tag: friction: a necessary evil

Questions Related to friction: a necessary evil

A coin flicked across a table will stop, because :

physics friction advantages and disadvantages of friction merits and demerits of friction and methods to reduce it friction: a necessary evil

  1. It is heavy

  2. No force is acting on it

  3. Earth attracts the coin

  4. Table exerts a frictional force

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Correct Option: D
Explanation:

According to the first law of motion a body will remain in the state of rest or of uniform motion until or unless compelled by an external force.

In this case the coin will stop because an external force is exerted in the form of frictional force by the table that opposes the motion of the flicked coin.

Hence, correct answer is option $D$

The application of decreasing friction includes :

physics friction advantages and disadvantages of friction merits and demerits of friction and methods to reduce it friction: a necessary evil

  1. Ball bearing used in moving parts of a machine

  2. The streamlined shape of an aircraft

  3. The layer of air between the hull of a hovecraft.

  4. None of these.

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Correct Option: A,B,C
Explanation:

The application of decreasing friction is
(i) Ball bearings used in moving parts of a machine.
(ii) The stream lines shape of an aircraft.
(iii) The layer of air between the hull of a hovecraft.

Which of the following are done to increase  friction?

physics friction advantages and disadvantages of friction merits and demerits of friction and methods to reduce it friction: a necessary evil

  1. Making groove in the shoes

  2. polishing rough surface

  3. using ball bearing in wheels

  4. Creating an air cushion

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Correct Option: A
Explanation:

Soles of shoes are grooved because the grooves increases the friction and gives the good grip to the person while walking with shoes