how is lift force proportional to speed up?

thebluser

i know that if i have a greater lift force, there will be a greater speed upwards, but i don't know to calculate a speed of something upwards. is this even possible to calculate? if it's not, can you give a calculation example??

CWatters

Work out the net force acting on the object in the vertical direction..

Net Force = Lift - Weight

Then apply Newton..

Net Force = mass * acceleration

If lift = weight then there is no net force acting on the object so it's vertical velocity will be constant (eg acceleration = 0).

thebluser

is weight the atmospheric pressure or how much the body weighs? just want to make sure.

rcgldr

By definition, lift is perpendicular to the direction of travel (with respect to the air), so it only changes direction, not speed. If a plane is in a steady vertical climb at some constant angle θ above horitzontal, with a vertical speed component of speed x sin(θ), then there needs to be enough thrust and lift so that the vertical components of thrust and lift equal the weight of the aircraft:

thrust x sin(θ) + lift x cos(θ) = weight.

thebluser

okay then, thank you all!