Question

1.a cork floats while a nali sink water give reason?

2.why does a block of plastic released under water come up to the surface of water?

3.take two open metal cylinder of same radius but of different heights place them vertically in a water beaker

a)do both submerge in water to the same level

b)can you find the reason?

4.why an object submerged in liquid appears lighter in comparison to its weight in air?give one example to support your answer.

5.fill water in glass ,take a small plastic ball ,using your finger ,when the plastic ball is completly under water.

Answer 1

a cork floats on water but an iron nail sinks because the density of iron nail is more than the cork

The density of plastic is less than that of water, so the force of buoyancy on plastic block  will be greater than the weight of plastic block displaced. Hence, the acceleration of plastic block will be in upward direction, and comes up to the surface of water

they seem to feel lighter, though, because of buoyancy. Archemedes's principle states that the force pushing on an object under water, is equal to the mass of the water it has pushed out of the way. So things apear lighter because the water is actually helping to push it up.

the plastic ball will not go into the water because the density of ball is very less due to the air in it so it will float on the surface of water

Answer 2

Answer:

The buoyant force acting on the block of plastic is more than its weight. As a result of this, it comes up when released under water. The cause of this larger buoyant force on the block of plastic is due to its density being smaller than that of water.