What is the force you need to use on the piston?

[campa]

If there is an ordinary sprayer (you know with the piston on one side and a bottle which has liquid inside it and is connected to the piston's tube by a tube which goes inside the liquid) and the air resistance on the piston when you try to push it is given (lets say F) what is the force you need to use on the piston?

Should the answer to this be F?

 

[SGT]

The force should be greater than F. You must use a force F to overcome the air resistance plus a force F₁ to accelerate the liquid out of the recipient.

 

[sir-pinski]

No, the force required to push the piston will be greater than F because you need to overcome both the air resistance and the resistance from the liquid inside the bottle. The exact force needed will depend on factors such as the viscosity of the liquid and the size of the piston, but it will definitely be greater than just the air resistance.