CBSE Important Questions(long questions) for Gravitation

Given below are the Class 9 Science Important Questions for CBSE Important Questions(long questions) for Gravitation
a) Concepts questions
b) Calculation problems
c) Multiple choice questions
e) Fill in the blank's
1. State the mathematical formula that relates thrust and pressure. List the factors on which the pressure depends and explain how it depends on them?
2. Differentiate between thrust and pressure?
3. The pressure exerted by a cube of side 0.03m on a surface is Pa. Calculate the thrust exerted by the cube?
4. Why does a block of plastic releases underwater come up to the surface of water?
5. The mass of a block made of certain material is 13.5 kg and its volume is 15*10-3 m3. Will the block float or sink in water?
6. The volume of a 350g sealed tin is 200cubic cm. Find the density of the tin in g/cc. Also find the density n SI unit?
7. A force of 250N acts on a surface of area 15cm2. Calculate thrust and pressure?
8. A solid weighs 50 gf in air and 44 gf when completely immersed in water. Calculate:
a) the upthrust
b) the volume of the solid
c) the relative density of the solid
9. A force of 400N acts on a surface of area 25cm2. Calculate thrust and pressure? Calculate the changed pressure if the force now is made to 600N?
10. Why are railway tracks laid on large sized concrete sleepers?
11. While drawing water from a well, the bucket of water appears to be heavier as it comes out of the water?
12. A piece of iron weighs 44.5gf in air, 39.5 gf in water and 40.3  gf in an oil. Find:
a) the relative density of iron.
b) the density of oil  in SI unit. What assumption have you made in your calculation?
13. A solid weighs 200 gf I air, 160 gf in water and 170 gf in a liquid. Calculate the relative density of the solid and that of the liquid?