When an object is thrown up, the force of gravity

When a fruit falls from a tree,

The force of gravitation between two bodies varies with r as

At which of the following locations, the value of g is the largest?

Why does a block of plastic released under water come up to the surface of water?

Name the instrument which is used to determine the density of a liquid.

Name the scientist who first determined the value of G experimentally. What is the values of G accepted presently?

A coin and a piece of paper are dropped simultaneously from the same height. Which of the two touch the ground first? What will happen if they are dropped in vacuum? Give reason for your answer.

What do you mean by the weight of an object on the moon? Why is the weight of an object on the moon is less than that on the earth?

Take a beaker filled with water. Take a piece of cork and an iron nail of equal mass. Place them on the surface of water. What happens. Explain.

Write two applications of Archimedes' principle.

At what height from the surface of g the earth, will the value of g be reduced by 36% from the value at the surface? Radius of the earth = 6400 km.

State Archimedes' principle? Write two applications of Archimedes' principle.

If a fresh egg is put into a beaker filled with water, it sinks. On dissolving a lot of salt in the water, the egg begins to rise and floats. Why?

Two different bodies are completely immersed in water and undergo the same loss in weight. Is it necessary that their weights in air should also be the same? Justify your answer.

What height above the surface of the earth, the value of g becomes 64% of its value at the surface of the earth? Take, the radius of the earth = 6400 km

Prove that, if a body is thrown vertically upwards, then the time of ascent is equal to the time of descent.

Hemlata had a bad experience during the take off of the plane when she boarded it for the first time. Her friend assisted and helped her during the landing of plane. She told her to fasten the seat belt and involved her in gossip. Hemlata faced less problems while landing of the plane.
Read the above passage and answer the following questions:
(i) Why do we tie our seat belts in moving cars or landing/take off of the plane?
(ii) What is free fall?
(iii) What value of Hemlata's friend is seen in this act?

What happens to the force between two objects, if
(i) the mass of one object is doubled?
(ii) the distance between the objects is doubled and tripled?
(iii) the masses of both objects are doubled?

State any three differences between mass and weight.