Tag: friction: a necessary evil

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

You are marooned on a frictionless horizontal surface and cannot exert any horizontal force by pushing against the surface. How can you get off ?

  1. by jumping

  2. by spitting or sneezing

  3. by rolling your body on the surface

  4. by running on the plane
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

By spitting or sneezing we can get off.

Since there is no friction present we need to spit or sneeze which will produce a suitable friction to get off. Also this will produce a momentum in opposite direction which will help us to move in opposite direcdtion.

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

Friction is a/an

  1. self-adjusting force

  2. necessary evil

  3. important force in daily life

  4. all the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
  1. Static friction is considered a self adjusting force because it wants the object to remain at rest and not move. Therefore, if an external force is applied, the static force will be equal to the magnitude of external force, until it surpasses the threshold of the motion. Hence friction is a self-adjusting force.
  2. If there is no friction between any two surfaces in contact , then we will not be able to walk properly on the earth. Hence friction is necessary, But too much friction will reduce the efficiency of machines. Hence friction is a necessary evil.
  3. Friction allows us to hold anything, pick up anything , allows us to go anywhere . Same goes with riding a car or a bike. Thus friction is important force in our daily life.
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

  3. Ambiguous

  4. Data insufficient
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Friction is the force that resists motion when the surface of one object comes into contact with the surface of another. In a machine, friction reduces the mechanical advantage , or the ratio of output to input an automobile, for instance , uses one-quarter of its energy on reducing friction. Hence the efficiency of machine is reduced due 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. <span>S will begin to slip on P</span>

  2. <span>P will begin to move back wards</span>

  3. <span>the speed of s will decrease, and its angular velocity will increase</span>

  4. <span>there will be no charge in the motion of S and P will still be at rest</span>
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.