1. ARMY PUBLIC SCHOOL, RAKHMUTHI
UNIT: GRAVITATION(PHYSICS)
Date: 16 oct- 2020 SUBJECT INCHARGE: MISS RITIMA
EXTRA QUESTIONS:
Q1.What will happentothe gravitational force betweentwobodiesif the massof one bodyisdoubled?
Ans:If the massof one bodyis doubled,force isalsodoubled.
Q 2. Why‘G’ is calledthe universal gravitational constant?
Ans:The constant‘G’ isuniversal because itisindependentof the nature andsizesof bodies,the space where theyare
keptand at the time at whichthe force is considered.
Q3.Who formulatedthe universal lawof gravitation?
Ans:Isaac Newton
Q4. How isgravitationdifferentfromgravity?
Ans:Gravitationisthe force of attractionbetweenanytwobodieswhile gravityreferstoattraction betweenanybody
and the earth.
Q5. If the mass of a body is9.8 kg on the earth,whatwouldbe itsmass on the moon?
Ans:It will remainthe same onthe moon,i.e.,9.8 kg.
Q6.Do fluidspossessweight?
Ans:Yes,fluidshave weight.
Q7. Why can one jumphigheron the surface of the moon thanon the earth?
Ans:Because the value of accelerationdue togravity(g) onthe moon’ssurface isnearlyl/6thtothat of the surface of the
earth.
Q8. Suppose gravityof earthsuddenlybecomeszero,thenwhichdirection will the moonbegintomove if noother
celestial bodyaffectsit?
Ans:The moonwill begintomove ina straightline inthe directioninwhichitwasmovingatthat instantbecause the
circularmotionof moon isdue to centripetal force providedbythe gravitationalforce of the earth.
Q9.The earth isacted uponby gravitationof sun,eventhoughitdoesnotfall intothe sun.Why?
Ans:The gravitational force isresponsible forprovidingthe necessarycentripetal force whichallowsthe earthtomove
aroundthe sunat the definedpathororbit.So, the earthdoesnot fall intothe sun.
Q10. If the small andbigstonesare droppedfromthe roof of a house simultaneously,theywill reachthe groundatthe
same time.Why?
Ans:The accelerationdue togravitydoesnotdependuponthe massof the stone or body.Both the bodiesfall withthe
same accelerationtowardsthe surface of the earth.Thusa bigstone will fall withthe same accelerationasasmall stone.
So,both the stoneswill reachthe groundat the same time whendroppedsimultaneously.
Q11. The earth attracts an apple.Doesthe apple alsoattractthe earth?If it does,whydoesthe earthnot move towards
the apple?
Ans:Accordingto Newton’sthirdlawof motion,actionandreactionare equal andopposite.Itmeansthatthe force on
the apple due to earth’sattractionisequal to thaton the earth due to apple’sattraction.Butwe know,acceleration ∝
1/m. Asthe massof the earthis verylarge as comparedto that of the apple,the accelerationexperiencedbythe earth
will be sosmall thatit will notbe noticeable.
Q12.Mentionany fourphenomenathatthe universal law of gravitationwasable toexplain.
Ans:The universal lawof gravitationwasable toexplainsuccessfully
the force that bindsus to the earth.
the motionof the moonaroundthe earth.
the motionof planetsaroundthe sun.
the tidesdue to the moonand the sun.
Q13. Whendoesan objectshowweightlessness?
Ans:Weightlessnessisastate whenan objectdoesnotweighanything.Itoccursonlywhena bodyisin a state of free fall
underthe effectof gravityalone.
Q14.Why doesa bodyreach the ground quickeratpolesthanat the equatorwhendroppedfromthe same height?
Ans:The accelerationdue togravityismore at the polesthanat the equator.The time takenfora bodyis lessif the
accelerationdue togravityismore whenthe initial velocitiesandthe distance travelledare the same.So,whendropped
fromthe same heightabodyreachesthe ground quickeratthe polesthanat the equator.
