# Momentum balance derivation in equations

by Fishinev
Tags: balance, fluids, head, mechanics, momentum
 P: 2 I'm a little confused, in my fluid mechanics course we've covered many equations and they are all derived using an x-direction fluid flow. If I was to use these in a system in which fluid flowed in the y-direction would I have to re-derive them? Or would it be more of a case of using a horizontal system in a vertical direction?
HW Helper
Thanks
P: 26,167
Hi Fishinev! Welcome to PF!
 Quote by Fishinev I'm a little confused, in my fluid mechanics course we've covered many equations and they are all derived using an x-direction fluid flow.
Do you mean that the entire flow is horizontal, so that gravity doesn't have to be taken into account?

In that case, if you want to apply the equations to a vertical system, you'll need extra (ρgh) terms to deal with gravity.
P: 5,462
 In that case, if you want to apply the equations to a vertical system, you'll need extra (ρgh) terms to deal with gravity.
If this is a gas dynamics question you can usually ignore body forces such as gravity at chemical engineering scales.

If this is a liquids questions then a body force such as gravity may well come into play.

Remember in chemical engineering other body forces are often also in play.

 Related Discussions General Engineering 0 Advanced Physics Homework 2 Chemistry 8 Chemistry 3
{"extraction_info": {"found_math": false, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.8343667984008789, "perplexity": 890.8220423205843}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2014-15/segments/1397609526102.3/warc/CC-MAIN-20140416005206-00317-ip-10-147-4-33.ec2.internal.warc.gz"}