NCERT Solution: Gravitation
The gravitational of the sun provides the necessary centripetal force to keep the earth in its orbit. This counters the centrifugal force which arises due to circular motion of the earth. Thus, earth remains on its orbit without either falling into the sun or going away tangentially to its orbit.
The weight will become 16 times.
F α 1/d2
This hypothesis is not correct. The two bricks, like a single body, fall with
the same speed to reach the ground at the same time in case of free-fall. This
is because acceleration due to gravity is independent of the mass of the falling
body
Ratio will not change in either case because acceleration remains the same. In
case of free-fall acceleration does not depend upon mass and size
(b) A ball weight 4 kg of density 4000 kg m-3 is completely immersed in water of density 103 kg m-3. Find the force of buoyancy on it. (Given g = 10 ms-2.)
Ans. (a) (i) The cube will experience a greater buoyant force in the
saturated salt solution because the density of the salt solution is greater than
that of water.
(ii) The smaller cube will experience lesser buoyant force as its volume is
lesser than the initial cube.
(b) Buoyant force = weight of the liquid displaced
= density of water � volume of water displaced �g
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