Question

we see many children to throw rock fastly in pond and this rock hope in the pond why the rock not sink in that pond why? explain briefly?

Answer 1

We throw that rock only which has got a pointed end at one of the ends. when we throw it the pointed end goes first and due to the bouyant force, the rock tries to gets flat and the pointed end rises slightly above. Now due to inertia the rock again flies above the water and the same process goes on and on. every time it hits the water it looses some of its kinetic energy which becomes potential energy and is transferred to the water. hence after losing sufficient energy or say after when the inertia becomes smaller than the total weight of the rock it finally stops and sinks inside the water.