# Acceleration and Velocity

## Main Question or Discussion Point

I can't belive I don't remember this. Is it possible to move upwards with a constant velocity? For example, if a block weighs 20 newtons, and I want it to go at a constant velocity of 5 m/s , could I do that with a constant force? For some reason I don't think I can, but maybe I'm just screwing myself up somewhere...

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HallsofIvy
Homework Helper
Force= mass times acceleration. In order that something move with constant velocity it is necessary that the acceleration be 0 and so that the net force be 0. If an object weight 20 N. that means that there is a force of 20 Newtons downward. To balance that and get a net force of 0, you need an upward force of 20 N also. Notice that the "5 m/s" doesn't come into that. In order to move an object weighing 20 N upward at 5 m/s you must first apply a force greater than 20 N upward so there is an acceleration upward. When the speed gets to 5 m/s then you must reduce the upward force to exactly 20 N to keep that constant speed.

dextercioby
Homework Helper
Incidentally,your case would work out fine,if you were to drag the body with a constant force which would balance the friction force perfectly (i.e.no vertical movement).

Daniel.

krab