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i just tried Fg=Gm1m2/r^2 and that doesn't work either 9.8=6.67^-11(5.99x10^24)/r^2

so is this just a gravitational potential near Earth question ?

Q: a 4.6 kg rocket is launched directly upward from Earth at 9 km/s . What altitude above Earth's surface does the rocket reach? Relevant equations: v=\sqrt{2Gm/r} Eg=Gm1m2(1/r1-1/r2) my attempt: i figured i should use the first equation which contains velocity so i did...

i figured to find the net force it would be the force of gravity minus the force of the string, Fnet=Fg-Fs Fnet=mg-kx Fnet=2.89kg(9.8m/s^2)-(18.7N/m)(0.1m) Fnet=28.322-1.87 Fnet=26.452 N

question: a grapefruit of mass 289g is attached to an unstretched vertical spring of force constant 18.7 N/m, and is allowed to fall. a) determine the net force and the acceleration on the grapefruit when it is 10.0 cm below the unstretched position and moving downward. b)air resistance...