# Can drag force and lift force be in the same direction here:

Roul
In the attached picture, can I say that there is a lift force in the Y-direction, and a drag force too in the same Y-direction?

FL proportional to V_fx2 ?

FD proportional to V_py2 ?

Is this equation of motion for the Y-direction correct here: ma = − mg − FD + V(rho)g + FL

The lift force is because of the horizontal flow which is in fact lifting the particle (lets assume there is some small velocity gradient around the particle, as the particle bottom experiences zero flow velocity and particle top experiences the flow velocity), and the drag force is due to the resistance to the particle's upward motion. Is this correct to say?

Please assume that the picture is correct, and such an observation was made.

https://imgur.com/x099TgP

https://imgur.com/x099TgP

https://imgur.com/x099TgP

can I say that there is a lift force in the Y-direction, and a drag force too in the same Y-direction?
Lift and drag are perpendicular to each other, but can both have a positive Y-component.

Roul
Lift and drag are perpendicular to each other, but can both have a positive Y-component.

So the lift force will be in the Y-direction, but the drag force will be at an angle (say theta) to the vertical direction, in between the horizontal flow velocity and the vertical particle velocity. So in my equation can I use FL and FDcos(theta) and rest will be the same, right?

So the lift force will be in the Y-direction, but the drag force will be at an angle (say theta) to the vertical direction,
Lift and drag components are perpendicular to each other per definition. Their orientation depends on what you consider as the reference flow direction.