Which object is in static equilibrium

Which force is most responsible for binding together an atom's protons and neutrons? electrostatic gravitational nuclear magnetic

Ahot-air balloonist, rising vertically with a constant speed of 5.00 m/s releases a sandbag at the instant the balloon is 40.0 m above the ground. after it is released, the sandbag encounters no appreciable air drag. compute the velocity of the sandbag at 0.250 s after its release.

Which one of the following research methods can show cause and effect