Gravitation-by-Bindu

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Dear Student, Read question and answers

Bindu D B

SNHSS

N. PARAVUR

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Q1. When a body is taken from the equator to the poles, its weight .... 

Answer : Increase

Hint : Because acceleration due to gravity g  increases ,
          hence weight =mg increases 

Q2. If the earth shrinks suddenly (without changing mass) to half of its
       present radius, the acceleration due to gravity will be ... 

Answer : 4g

Hint : If radius shrinks half of its present value then g will become four times


Q3. The diameters of the two planets are in the ratio 4:1 and their mean densities in the ratio 1:2.the acceleration due to gravity on the planets will be in the ratio... 

Answer :  2:1

Hint : g=4GπρR/3 where ρ is density , g1/g2 = ρ1R1 / ρ2 R2 =1*4 /2*1 =2/1


Q4. The velocity with which a projectile must be fired to escape
        from the earth does not depend upon... 

Answer : Mass of projectile

Hint : Ve= (2gR)1/2, independent of mass of projectile 

Q5. In case of an orbiting satellite, if the radius of orbit is decreased... 

Answer : KE increases

Hint : KE=GMm/2r

Q6. Velocity of the planet when it is closest to the sun is ...

Answer : Maximum

Hint :  Velocity of the planet is inversely proportional to distance of the

           planet from the sun

Q7.  Two spheres of masses M and m are situated in air and gravitational force between them is F. The space around the mass is now filled with a liquid of specific gravity  3. The gravitational force now will be...

Answer : F

Hint : The gravitational force does not depend of the medium between the masses


Q8. What is the value of acceleration caused by the force
       
      of gravity on a stone placed on groiund ?


Answer : 0



Hint : Stone will experience force of gravity, but acceleration is zero, as this
          force is balanced by  reaction of ground

Q9. For a geostationary satellite , height above the earth is ....

Answer : 35800 km



Q10.  The ratio of the magnitude of potential energy and kinetic energy

 of a satellite is ...

Answer : 2:1 


Hint :   

 PE =  G M m / ( R + h) and KE = GMm / 2 ( R + h )

so, PE / KE = 2/1

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