Page 11 - Simplied Force

SIMPLIFIED COURSE ON SEE SCIENCE : CHAPTER- FORCE

Ans: The magnitude of the acceleration due to gravity increase if radius of the earth is decreased by
keeping its mass constant.

14) What is gravitational constant? Write its S.I. unit and value?

Ans: Universal gravitational constant 'G' can be defined as the force of gravitation that is exerted between
two unit masses which are separated from one another by a unit distance.

2
-2
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2
-2
Its S.I. unit is Nm kg and its value is 6.67 x 10 Nm kg .
15) At what condition the value of acceleration due to gravity is approximately zero, while getting
down from parachute?
Ans: When a parachute falls down, it is pulled downward by a certain force of gravity. Air also provides
resistance and opposes the downward movement of parachute. When air resistance is equal to the pulling
force of gravity of the earth, the acceleration of the falling parachute is approximately zero.

16) What is gravity?
Ans: The force of attraction of the heavenly bodies to any object towards its Centre is called gravity.

17) We do not get hurt, when we jump with parachute?

Ans: On the earth there are lavers of different eases. When a parachutist jumps out of the aeroplane,
parachute opens and expands due to which air exert large resistance on the parachute so that parachute
fall down slowly and uniformly. Hence, the parachutists do not get hurt, when they jump with parachute
out of an aeroplane.

18) Define acceleration due to gravity (g). Write the S.I. unit of weight of an object.
Ans: The uniform acceleration produced in a freely falling body due to the gravitational pull of the earth
towards its Centre is called acceleration due to gravity.

The S.I. unit of weight of an object is Newton (N).

19) State Newton’s Universal Law of Gravitation.

Ans: It states that, "everybody in the universe attracts every other body with a force which is directly
proportional to the product of their masses and inversely proportional to the square of the distance
between their centers."
20) A piece of stone and a feather are dropped from the same height at lunar surface, which one
will reach on the surface fast and why?

Ans: As we know that there is no atmosphere in the lunar surface. When a piece of stone and a feather
are dropped from the same height at lunar surface, they fall simultaneously due to free fall. Because
acceleration produces in the freely falling bodies, whatever their masses, are the same in the absence of
air resistance.

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