Motion Under Gravity

Total Questions: 41

1. Who among the following anticipated Newton by declaring that all the things gravitate to the earth. [I.A.S. (PRE) 1995]

(a) Aryabhatta
(b) Varahamihira
(c) Buddhagupta
(d) Brahmagupta

Correct Answer: (d) Brahmagupta

Solution:Brahmagupta was a great 7th century mathematician and astronomer .He was born in Bhinmal in Rajasthan .He is best known for his Brahmasphuta Siddhanta in which he declared that all things gravitate to the earth.

2. Who gave the theory of gravity [M.P.P.C.S.(PRE) 2010]

(a) charles newton
(b) charles babbage
(c) Issac newton
(d) john adams

Correct Answer: (c) Issac newton

Solution:In 1687 issac newton published his law of gravitation in his book mathemetical principal of natural philoshopy. Newton proposed that everbody in the universe attracted to each other body with a force that is directly proportional to the product of their masses and the inversely proportional to the square of the distance between them. In mathematical term it is written in the term of
F=G{m1*m2/r²}
where r= the distance between both the masses
G= Gravitational constant.

3. Who propounded the universal law of gravitation ? [M.P.P.C.S.(PRE) 2000 , Uttarakhand U.D.A./L.D.A.(PRE) 2007]

(a) Newton
(b) Galileo
(c) Copernicus
(d) Einstein

Correct Answer: (a) Newton

4. Astronaut in the space can not stand erect. This is because in space - [U.P.P.C.S.(MAINS) 2007]

(a) there is a no gravity
(b) viscous of the atmosphere are very strong
(c) solar wind exert an upward forces
(d) atmosphere pressure is very low

Correct Answer: (a) there is a no gravity

Solution:In space astronauts cannot stand erect because there is no gravity or microgravity. In this condition people or objects appear to be weightless. Microgravity effects the human body in several ways.For example muscle and bones can become weaker without gravity.

5. if an apple is released from an orbiting spaceship it will- [U.P.P.C.S.(pre) 2010]

(a) fall towards the earth
(b) move at a lower speed
(c) move along with spaceship at the same speed
(d) move at a higher speed

Correct Answer: (c) move along with spaceship at the same speed

Solution:If an apple is released from an orbiting spaceship it will move along with the spaceship at the same speed.

6. The leaning tower of Pisa does not fall because- [U.P.P.C.S.(pre) 2009]

(a) it is tapered at the top
(b) it covers a large base area
(c) it centre of gravity remains at the lowest position
(d) The vertical line through the centre of gravity of the tower falls within its base

Correct Answer: (d) The vertical line through the centre of gravity of the tower falls within its base

Solution:Anything will remain the stable as long as the vertical line through the centre of gravity lies on its base . The centre of gravity is that point where the whole mass of the body is supposed to concentrated.Till today vertical line through the centre of gravity of the tower falls within its base of this tower.That is why it has not fallen.

7. If the distance between the earth and the sun were twice what it is now the gravitational force exerted on the earth by the sun would be - [U.P.P.C.S.(MAINS) 2009]

(a) twice as large as it now
(b) four times as large as it now
(c) one fourth of what it is now
(d) half of what it is now

Correct Answer: (c) one fourth of what it is now

Solution:Let the present distance between the earth and the sun is 'r' then according to the newton universal law of gravitational the gravitational force imposed by the sun on the earth :
F1=G{MsMe/r²} ------ (1)
Ms=mass of the sun
Me=mass of the earth
G=gravitational constant
if the distance between the earth and the sun were twice then,
F2=G{MsMe/(2r)²}=G{MsMe/4r²} ------(2)
from equation (1) and (2)
F1/F2=4/1⇒4F2=F1
∴ F2=1/4F1

8. If an object falling from the above its weight remains- [M.P. P.C.S.(PRE) 1992]

(a) zero
(b) same
(c) change
(d) none of the above

Correct Answer: (b) same

Solution:In ideal condition (when air resistance is negligible ) if an objects is failing from the above its weight remains same because mass of the object and the gravity remains unchanged.

9. If a feather a rubber ball and a wooden a ball are falling freely simultaneously from the same height in vacuum then ; [67th B.P.S.C. (PRE) 2022]

(a) the feather will reach at the ground first
(b) the rubber ball will reach tat the ground first
(c) the wooden ball will reach tat the ground first
(d) all the three will reach at the ground together
(e) nine of the above /more than one

Correct Answer: (d) all the three will reach at the ground together

Solution:The feather, the rubber and wooden ball will fall with the same speed and reach the ground together because there is no air resistance in the vacuum and gravitational force acts same on all the objects.Hence every object undergoes free fall in the vacuum with the same acceleration.

10. If piece of equal size of woods wax and the iron falling from a same height ,which one will reach the surface of the earth first ? [R.A.S./R.T.S (PRE) 1992]

(a) wood
(b) wax
(c) iron
(d) reach at the same time

Correct Answer: (d) reach at the same time

Solution:In ideal condition (when air resistance is negligible ) if an objects is failing from the above its weight remains same because mass of the object and the gravity remains unchanged.

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Motion Under Gravity