Physical Properties of Matter (Physics)

Total Questions: 54

41. Why does an iron nail float on mercury while it sinks in water? [U.P.P.C.S. (Pre) 1994]

Correct Answer: (c) Iron has greater density than water and lesser than mercury.
Solution:

An iron ball floats on mercury but gets immersed in water because the relative density of mercury is greater than the relative density of iron. However iron has a higher density than water, so it gets immersed in water. Thus statement (A) is correct but reason (R) is incorrect.

42. A needle sinks in water whereas a ship made of iron floats on it because : [U.P. Lower Sub. (Spl) (Pre) 2004]

Correct Answer: (d) Relative density of the needle is greater than that of water displaced by it
Solution:

Relative density is defined as a ratio of the density of a particular substance with that of water. The relative density of pure water is 1. The substance having the relative density less than I will float in water, while substance having the relative density more than I will sink in water.

The ship is designed in such a way that its effective density (m/v) is less than the density of water and the weight of the water displaced by the ship is equal to its weight, so it floats upon the water. But the density of iron needle is much larger than the water, so it sinks easily.

43. An iron needle floats on the surface of water due to- [U.P.P.C.S. (Mains) 2012]

Correct Answer: (b) Surface tension
Solution:

An iron needle can float on water due to the surface tension of water because upward force on the needle due to surface tension balances the weight of the needle.

44. While lifting a bucket of water from a well, we feel that the bucket: [U.P.P.C.S. (Pre) 2009]

Correct Answer: (a) Becomes heavier above the surface of water
Solution:

According to the Archimedes' principle of flotation, object appears to be heavier in the air than inside the water or they appear to be less heavy in the water. It is because water exerts an upward force on the objects immersed in it. This reduction is equal to the weight of the fluid that body displaces.

45. 200 gm of water is filled in a weightless balloon. Its weight in water will be [U.P.R.O/A.R.O (Mains) 2014]

Correct Answer: (a) Zero
Solution:

Weight of balloon in water = Weight - Upthrust

= 200 - 200 = 0

The balloon is weightless.

46. The clouds float in the atmosphere because of their low : [I.A.S. (Pre) 1995]

Correct Answer: (d) Density
Solution:

Clouds form when the invisible water vapour in the air condenses into visible water droplets. They are so small that the effect of gravity on them is negligible. Thus the clouds float in the atmosphere because of their low density.

47. While floating in a sea what part of an iceberg is above the surface of the sea? [U.P.P.C.S. (Pre) 2005]

Correct Answer: (a) 1/9
Solution:

When pure water changes into the ice at 4°C, the density of ice so formed is 9/10th of the density of water. Therefore, in pure water, 90% part of the ice must be below the surface of the water and remaining 10% part must be above the surface.

Sea water has high density (salty) water but the ice formed by it is pure and not salty. Therefore, while floating in a sea about 1/8 to 1/9th part of an iceberg is above the surface of the sea.

48. An ice cube is floating in a glass of water. What happens to the water level when the ice melts? It- [M.P.P.C.S. (Pre) 2008]

Correct Answer: (c) Remains the same
Solution:

According to Archimedes' principle, floating object displaces an amount of water equal to its own weight. Thus, the water level remains the same when the ice cube melts.

49. A piece of ice is floating in a beaker containing water up to its brim. When whole of the ice melts : [67ᵗʰ B.P.S.C. (Pre) 2022]

Correct Answer: (d) the water level will not change
Solution:

According to Archimedes' principle, floating object displaces an amount of water equal to its own weight. Thus, the water level remains the same when the ice cube melts.

50. A body floats at 4°C water. If temperature reaches 100°C then- [M.P.P.C.S. (Pre) 1999]

Correct Answer: (a) The body will sink
Solution:

When the water is heated, its density decreases. The density of the water at 100°C is at the lowest, so the body will sink. Water density is maximum at 4°C, so the body floats.