Tag: friction

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Questions Related to friction

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

A sphere $S$ roll without slipping, moving with a constant speed on a plank $P.$ The fraction between the upper surface of $P$ and the sphere is sufficient to prevent slipping, while the lower surface of $P$ is smooth and rests on the ground. Initially, $P$ is fixed to the ground by a pin $N.$ If $N$ is suddenly removed:

  1. S will begin to slip on P

  2. P will begin to move back wards

  3. the speed of s will decrease, and its angular velocity will increase

  4. there will be no charge in the motion of S and P will still be at rest
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

When the pin is removed, the sphere continues rolling without slipping because friction between the sphere and upper plank surface prevents relative motion. Since the lower surface of plank P is smooth and there's no external horizontal force on the sphere-plank system, the center of mass has no horizontal acceleration. The plank remains stationary as the sphere maintains its rolling motion.

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

Why do we sprinkle powder before playing carroms?

  1. To increase friction

  2. To decrease friction

  3. To increase or decrease the friction depending on the type of the game played

  4. None of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

It is done just to reduce the friction. On microscopic level, the powder particles offer rolling friction to the striker because of which the striker can be rolled around smoothly.

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

State whether the statements are true or false:
Oil is used to reduce the friction on door hinges.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Lubrication is another way to make a surface smoother. A lubricant is a slippery substance designed to reduce the friction between surfaces, Since the door hinges are exposed to the atmosphere the chances of corrosion increases and the surface becomes irregular enough to promote friction. Applying oil on the door hinges can reduce the amount of friction and thus it will decrease it.

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

Friction should always be avoided.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
The given statement is false.
Friction is a necessary evil because without friction we will not be able to set our bodies in motion or stop the bodies which are in motion. Friction is absolutely necessary in our day to day activities. For eg it is the friction on the ground that helps us to walk and without friction it would not have veen possible to write on a paper.
Hence friction is important and cannot be avoided.
Multiple choice physics friction advantages and disadvantages of friction merits and demerits of friction and methods to reduce it friction: a necessary evil

The efficiency of machine is reduced due to friction.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Yes, the statement is true.

Friction introduces losses and decreases efficiency since friction generates heat which is an energy that should be converted in movement. That energy in the form of heat is a loss. Also friction increases increases the wear and tear of a machine thereby decreasing its efficiency.

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

A coin flicked across a table will stop, because :

  1. It is heavy

  2. No force is acting on it

  3. Earth attracts the coin

  4. Table exerts a frictional force
Reveal answer Fill a bubble to check yourself
D Correct answer
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 $D$

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

The application of decreasing friction includes :

  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.
Reveal answer Fill a bubble to check yourself
A,B,C Correct answer
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.

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

Which of the following are done to increase  friction?

  1. Making groove in the shoes

  2. polishing rough surface

  3. using ball bearing in wheels

  4. Creating an air cushion
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

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