Question #1068c

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Answer 1 · 2016-06-05T01:25:15

$"Option D"->"~~7.4(km)/s$

Let

Now we know

$"Centripetal pull on earth " = "Gravitational force acting between"$

$=>(mv^2)/(R+h)=(GmM)/(R+h)^2$

$=>(cancelmv^2)/cancel(R+h)=(GcancelmM)/(R+h)^cancel2$

$=>v^2=(GM)/(R+h))$

$=>v^2=(gR^2)/(R+h)......(1)$ $" "[ Since " " GM=gR^2]$

Now inserting the values in equation (1) we get

$=>v^2=(9.8xx10^-3(6400)^2)/(6400+900)$

$=>v=sqrt((9.8xx10^-3(6400)^2)/(6400+900))~~7.4(km)/s$