Wednesday, 13 May 2020

gravity - How gravitation affects tides


I know that tide is caused by the gravitational pull of moon but what I don't know is how it affects water. I have actually these doubts.




  1. Why does gravity of the moon creates tides only in water?




  2. Are there other things (other than water) where tides are created on earth ( I have heard that, in some moons of Jupiter tides(of ground) can be found on the surface due to Jupiter's gravity)?





  3. If we take a bowl of some length; lets say 30 cm diameter and fill it with water and keep it in a full moon night. Whether it will create tide?




  4. If moons gravitational pull can cause tides in seas, then why a sailor can't feel the gravitational pull of moon?





Answer



You ask:




How gravity of the moon creates tides only in water?



This is wrong. Tides are created by the moon on all materials on earth that have some elasticity. The raising and falling of the ground has been measured at the beams in CERN, for example. The solid ground tides are called earth tides and their height can be 40cm.



Is any things( other than water) also create tides in earth( i heard that some moons in Jupiter has tides(of ground) on the surface due to Jupiter's gravity)?



You mean "get tides", not "create tides". It is the moon mainly and not the water that creates the tides.


There is some effect in the tides from the large planets and the sun's gravitational field. That is why tide tables are needed. The source is not one. Yes there are tides on planets that have moons and some elasticity in their composition.



If we take a bowl of some length; lets say 30 cm diameter and fill it with water and kept it in a full moon night whether it will create tides?




You should measure the bowl during the tide cycle, which is close to a 12 hour one ; the full moon or not is a secondary effect. Look at the explanation in the link. You will need accurate measurements and to consult tide tables for your particular location.



If moons gravitational pull can cause tides in seas, then why a sailor cant feel the gravitational pull of moon?



The sailor and all of us feel the vector sum of the gravitational forces impinging on us at our location. One cannot distinguish the individual components unless on does a fit to the components of known gravitational sources. We are not equipped biologically for that , so it must not offer an evolutionary advantage :) . The water is lifted and the boat is lifted with the water, no?


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