Presentation which introduces hydrostatic pressure and buoyancy

1. 4. Pressure in fluids
1. Definition of pressure
2. Hydrostatic pressure. Siphon
3. Atmospheric pressure.
Torricelli experiment
4. Buoyancy
5. Pascal´s law
© Patricio Gómez Lesarri
© science.howstuffworks.com

2. 1. Definition of pressure
Force per unit of area
Concentration of force in a
point
Effect of a force in fluids
Units:
Pascal 1 Pa= 1 N.m-2
kPa, MPa
Atmosphere: 101300 Pa ≈ 100
kPa = 760 mm Hg
Bar 1 Bar= 100 kPa
© http://physics.wfu.edu
P =
F
S
© blogs.wwf.org.uk/

3. 2. Hydrostatic pressure
Why does water not fall ?
https://www.youtube.com/wa
Variables
Height
Liquid density
© www.tutiempo.net

4. 2. Hydrostatic law
Pressure doesn´t depend on
the amount of fluid
https://www.youtube.com/watch?v=J7ymn6f2Bl8
Paradoja de Pascal:
https://www.youtube.com/watch?v=EJHrr21UvY8© http://www.school-for-champions.com/
P = ρ.g.h
P =
mg
S
=
ρVg
S
= ρgh

5. 2. Siphon: communicating vessels
Vasos comunicantes
Sifón
https://www.youtube.com/w
Tubos en U
© fq-experimentos.blogspot.com

6. 2. Siphon misconceptions
© Lewis C. Epstein

7. 2. Siphon misconceptions
© Lewis C. Epstein

8. 2. Pressure misconceptions
© Lewis C. Epstein

9. 2. Pressure misconceptions
© Lewis C. Epstein

10. 3. Lab activity:
Presión hidrostática
Práctica virtual: buzo en el
mar :
http://webs.um.es/gregomc/LabESO/PresionMar/PresionMar.html
© Gregorio J Molina Cuberos
http://webs.um.es/gregomc/LabESO/index.htm

11. 3. Atmospheric pressure.
Torricelli´s experiment
Torricelli´s experiment
https://www.youtube.com/watch?v
https://www.youtube.com/watch?v
https://phet.colorado.edu/es/simul
http://www.kscience.co.uk/animatio
© http://www2.southeastern.edu/
P = ρ.g.h =13700kg.m−3
.9,8m.s−2
.0,76m =101300Pa

12. 3. Vacuum. Pressure difference
Gas occupies its own space
https://www.youtube.com/watch?v=Po1C5qk3pSQ
A net force is applied between
points at different pressures
https://www.youtube.com/
watch?v=_CXd2h5O8OU
https://www.youtube.com/
watch?v=28TIyWdfxxc
https://www.youtube.com/
watch?
v=qXclcimrmfI&index=13
1&list=PLC02CFDE5690E
4010

13. 4. Buoyancy
Does mandarines float?
Variables:
Mass
Fluid density
 Volume
© www.playdoughtoplato.com

14. 4. Archimedes´ principle
https://www.youtube.com
/watch?v=eQsmq3Hu9HA
https://www.youtube.com
/watch?v=VDSYXmvjg6M
Buoyant force applied to an
object equals the weight
of the displaced fluid
© Hila science
FB = ρ.V.g

15. 4. Archimedes misconceptions
© Lewis C. Epstein

16. 4. Archimedes misconceptions
© Lewis C. Epstein

17. 5. Pascal´s principle
The pressure applied to a
fluid is transmited
undiminished to every
point of the fluid and to the
walls of the container
https://www.youtube.com
/watch?
v=iD55ynlUH8g#t=14
https://www.youtube.co
m/watch?
v=8ma4kW3xVT0
© http://www.tutorvista.com

18. 5. Hydraulic jack
Hydraulic system which
allows to multiply forces
according to Pascal´s law
© hyperphysics.phy-astr.gsu.edu
P1 = P2
F1
S1
=
F2
S2