Question

If a planet has density equal to twice the density
of earth but radius equal to half of earth, then a
person weighing 72N on earth will weight how
much on that planet.
1)72N
2)36N
3)12N
4)8N


no spams plz..spams will be reported.. explain it properly plz plz...​

Answer 1

Answer is 8 N

Let the mass of earth be 'm' and density be 'p' and volume be 'v'.

Then mass of the earth will be m=pv.

Given,

p1=2p

V1=4/3pi(r/2)^3=v/8

then m1=2p×v/8=pv/4=m/4

F=G mM/r^2=72N

Therefore,

F1=GmM/4(3r/2)^2=4GmM/4×9×r^2=4×72/4×9=8N