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...