Motion under gravity and forces

[D. Wani]

If a body is falling downward under the effect of gravity(=mg) and someone applies a force(=mg) in the opposite direction (upward), then the body will continue moving downwards as the net force is zero. What would be the magnitude of the force applied such that the body would freeze in midair(if possible) and what would be the magnitude of the force applied such that the body would start moving upwards?

 

[mfb]

Those are not fixed force values. Force determines acceleration, not speed. If the acceleration is upwards, the body will get slower over time, stop, and then start moving upwards. The timescale depends on the force. To keep it at rest, the force has to drop to mg once the object stops.

 

[D. Wani]

Thank you