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Question: Answered & Verified by Expert
Two satellites A and B are revolving around a planet in coplanar and concentric circular orbits of radii R1 and R2 respectively in the same sense. Their respective periods of revolution are 1 hour and 8 hours respectively. The radius of the orbit of A is equal to 104 km. What is their relative speed when they are closest?
PhysicsGravitationJEE Main
Options:
  • A π×104 km h-1
  • B π2×104 km h-1
  • C 3π2×104 km h-1
  • D 2π×104 km h-1
Solution:
2589 Upvotes Verified Answer
The correct answer is: π×104 km h-1
By Kepler's third law T2R3 or T2R3=constant

T12T22=R13R23

164=R13R23

R1R2=14

R2=4R1=4×104 km

Distance travelled by A in one revolution is S1=2πR1=2π×104 km

v1=S1T1=2π×1041=2π×104 km h-1

Similarly, v2=S2T2=2π×4×1048=π×104 km h-1

V12=V1V2=π×104 km h-1

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