UPSC Exam  >  UPSC Questions  >  Why the needle of iron swims on water surface... Start Learning for Free
Why the needle of iron swims on water surface when it is kept gently ?
  • a)
    It will remain under the water, when it will displace more water than its weight
  • b)
    the density of needle is less than that of water
  • c)
    due to surface tension
  • d)
    due to its shape
Correct answer is option 'C'. Can you explain this answer?
Most Upvoted Answer
Why the needle of iron swims on water surface when it is kept gently ?...
Explanation:

When a needle of iron is kept gently on the water surface, it appears to float or swim instead of sinking. This phenomenon can be explained by the concept of surface tension.

Surface Tension:
Surface tension is the property of a liquid that allows it to resist an external force. It is caused by the cohesive forces between the molecules of the liquid. These cohesive forces create a thin film on the surface of the liquid, which acts like a stretched elastic sheet.

Reason for Needle Swimming:
The needle of iron swims on the water surface due to the surface tension of water. Here's a detailed explanation of why the correct answer is option 'C' (due to surface tension):

1. Surface Tension: When the needle is gently kept on the water surface, the surface tension of water comes into play. The molecules at the surface of the water experience a net inward force due to the cohesive forces between them. This force creates a stretched surface film.

2. Shape of the Needle: The shape of the needle plays a crucial role in this phenomenon. The needle has a relatively small contact area with the water surface due to its slender shape. This means that the surface tension forces acting on the needle are concentrated on a small area.

3. Upward Force: The surface tension forces acting on the needle create an upward force that is greater than the downward force of the needle's weight. This upward force allows the needle to float or swim on the water surface.

4. Displacement of Water: The density of the needle being greater than that of water (option 'B') is not the reason for its swimming. If the needle were denser than water, it would sink. Similarly, if the needle were to displace more water than its weight (option 'A'), it would also sink. It is the surface tension forces that counteract the weight of the needle and allow it to remain on the water surface.

Conclusion:
In conclusion, the needle of iron swims on the water surface when it is gently kept due to the surface tension of water. The cohesive forces between water molecules create a stretched surface film, and the shape of the needle allows it to experience an upward force greater than its weight, resulting in its floating or swimming behavior.
Explore Courses for UPSC exam

Top Courses for UPSC

Why the needle of iron swims on water surface when it is kept gently ?a)It will remain under the water, when it will displace more water than its weightb)the density of needle is less than that of waterc)due to surface tensiond)due to its shapeCorrect answer is option 'C'. Can you explain this answer?
Question Description
Why the needle of iron swims on water surface when it is kept gently ?a)It will remain under the water, when it will displace more water than its weightb)the density of needle is less than that of waterc)due to surface tensiond)due to its shapeCorrect answer is option 'C'. Can you explain this answer? for UPSC 2024 is part of UPSC preparation. The Question and answers have been prepared according to the UPSC exam syllabus. Information about Why the needle of iron swims on water surface when it is kept gently ?a)It will remain under the water, when it will displace more water than its weightb)the density of needle is less than that of waterc)due to surface tensiond)due to its shapeCorrect answer is option 'C'. Can you explain this answer? covers all topics & solutions for UPSC 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for Why the needle of iron swims on water surface when it is kept gently ?a)It will remain under the water, when it will displace more water than its weightb)the density of needle is less than that of waterc)due to surface tensiond)due to its shapeCorrect answer is option 'C'. Can you explain this answer?.
Solutions for Why the needle of iron swims on water surface when it is kept gently ?a)It will remain under the water, when it will displace more water than its weightb)the density of needle is less than that of waterc)due to surface tensiond)due to its shapeCorrect answer is option 'C'. Can you explain this answer? in English & in Hindi are available as part of our courses for UPSC. Download more important topics, notes, lectures and mock test series for UPSC Exam by signing up for free.
Here you can find the meaning of Why the needle of iron swims on water surface when it is kept gently ?a)It will remain under the water, when it will displace more water than its weightb)the density of needle is less than that of waterc)due to surface tensiond)due to its shapeCorrect answer is option 'C'. Can you explain this answer? defined & explained in the simplest way possible. Besides giving the explanation of Why the needle of iron swims on water surface when it is kept gently ?a)It will remain under the water, when it will displace more water than its weightb)the density of needle is less than that of waterc)due to surface tensiond)due to its shapeCorrect answer is option 'C'. Can you explain this answer?, a detailed solution for Why the needle of iron swims on water surface when it is kept gently ?a)It will remain under the water, when it will displace more water than its weightb)the density of needle is less than that of waterc)due to surface tensiond)due to its shapeCorrect answer is option 'C'. Can you explain this answer? has been provided alongside types of Why the needle of iron swims on water surface when it is kept gently ?a)It will remain under the water, when it will displace more water than its weightb)the density of needle is less than that of waterc)due to surface tensiond)due to its shapeCorrect answer is option 'C'. Can you explain this answer? theory, EduRev gives you an ample number of questions to practice Why the needle of iron swims on water surface when it is kept gently ?a)It will remain under the water, when it will displace more water than its weightb)the density of needle is less than that of waterc)due to surface tensiond)due to its shapeCorrect answer is option 'C'. Can you explain this answer? tests, examples and also practice UPSC tests.
Explore Courses for UPSC exam

Top Courses for UPSC

Explore Courses
Signup for Free!
Signup to see your scores go up within 7 days! Learn & Practice with 1000+ FREE Notes, Videos & Tests.
10M+ students study on EduRev