Jump to content
• 0

# Fluids and projectile motion

## Question

Hi, I'm really stuck on this problem and I don't know how to solve it. I have a syringe full of water laid horizontally at a height of 4,9 meters from the ground. I want to calculate the distance that the water coming out of the syringe travels before hitting the ground (it acts like a projectile). A pressure of 100 Pa is applied to the "back" of the syringe (the thing of the syringe that when pushed expels water). The diameter of the back is 1 cm whereas the diameter of the little exit at the front is 2 mm.

This is my strategy:

• I calculate the areas (by making sure to convert cm and mm to meters) and apply the continuity equation A1v1 = A2vso that I can find the ratios between the velocities.
• I then use Bernoulli's equation to find the final velocity of the water getting out of the syringe.
• Then I use one of the kinematics equations to find the distance travelled by the water using the final velocity of the syringe as the initial velocity of the projectile motion.

The problem is that I cannot find the final pressure in the Bernoulli's equation. What I mean by that is that I have this:

P1 + 1/2ρv12 + ρgy1 = P2 + 1/2 ρv22+ ρgy2

• ρgyand ρgycancel out
• To find v2 I need the final pressure P2 but I don't have it. How can I find it?

Thanks! I appreciate any help that comes my way.

## Recommended Posts

• 1

I would think the final pressure would be atmospheric...  🙂

#### Share this post

##### Share on other sites
• 0

Thanks Dan, wishing you & your family a great Christmas

#### Share this post

##### Share on other sites
• 0

All the best to you and yours as well!  Merry Christmas!

## Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Answer this question...

×   Pasted as rich text.   Paste as plain text instead

Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×

#### Terms of Use

The pages of APlusPhysics.com, Physics in Action podcasts, and other online media at this site are made available as a service to physics students, instructors, and others. Their use is encouraged and is free of charge. Teachers who wish to use materials either in a classroom demonstration format or as part of an interactive activity/lesson are granted permission (and encouraged) to do so. Linking to information on this site is allowed and encouraged, but content from APlusPhysics may not be made available elsewhere on the Internet without the author's written permission.

#### Copyright Notice

APlusPhysics.com, Silly Beagle Productions and Physics In Action materials are copyright protected and the author restricts their use to online usage through a live internet connection. Any downloading of files to other storage devices (hard drives, web servers, school servers, CDs, etc.) with the exception of Physics In Action podcast episodes is prohibited. The use of images, text and animations in other projects (including non-profit endeavors) is also prohibited. Requests for permission to use such material on other projects may be submitted in writing to info@aplusphysics.com. Licensing of the content of APlusPhysics.com for other uses may be considered in the future.

#### APlusPhysics Books

×
×
• Create New...