Advertisements
Advertisements
Question
A plastic cube is released into the water. Will it sink or come to the surface of the water?
Advertisements
Solution
When a plastic cube is released into water, it will come to the surface and float if its density is lower than the density of water. This happens because of buoyancy. Water exerts an upward buoyant force on the cube, and if this force is equal to or greater than the cube’s weight, the cube floats.
In this experiment, the plastic cube floats because it is less dense than water. In contrast, a glass cube usually sinks because its density is greater than that of water, so its weight is greater than the buoyant force acting on it.
RELATED QUESTIONS
In which direction does the buoyant force on an object due to a liquid act ?
How does the density of a body and that of a liquid determine whether the body will float or sink into that liquid?
What physical quantity is measured in bar?
Explain the following statement:
Sleepers are laid below the rails.
(i) The diameter of neck and bottom of a bottle are 2 cm and 10 cm, respectively. The bottle is completely filled with oil. If the cork in the neck is pressed in with a force of 1.2 kgf, what force is exerted on the bottom of the bottle?
(ii) Name the law/principle you have used to find the force in part (a).
What do you understand by the term upthrust of a fluid? Describe an experiment to show its existence.
A metal solid cylinder tied to a thread is hanging from the hook of a spring balance. The cylinder is gradually immersed into the water contained in a jar. What changes do you expect in the readings of the spring balance? Explain your answer.
The mass of a block made of certain material is 13.5 kg and its volume is 15 × 10-3 m3.
(a) Calculate upthrust on the block if it is held fully immersed in water.
(b) Will the block float or sink in water when released? Give a reason for your answer.
(c) What will be the upthrust on block while floating?
Take density of water = 1000 kg m-3.
Calculate the hydrostatic pressure exerted by water at the bottom of a beaker. Take the depth of water as 40 cm, the density of water 1000 kgm−3 and g = 9.8 ms−2.
Is thrust a scalar or vector quantity?
