CK-12 Physical Science Concepts - For Middle School

4.32. Pascal’s Law http://www.ck12.org

FIGURE 4.63

Hydraulic Brakes

A: The pressure exerted by the fluid on the brake shoes is applied over a larger area. When pressure acts over a larger
area, it increases the force (Force = Pressure×Area).

Hydraulic car lifts also use fluid to transmit pressure and increase force. The lifts are used to raise cars, which are
very heavy, so mechanics can work on them from underneath. Controls in airplanes use fluids to transmit pressure
and increase force so a flick of a switch can raise or lower heavy landing gear. To see animations of hydraulic
systems such as these, go to URLs:

• http://science.howstuffworks.com/transport/engines-equipment/hydraulic1.htm


• http://home.kpn.nl/RBrink1955/hydr_e.htm

For a dramatic demonstration of the use of hydraulics to increase force, watch Bill Nye the Science Guy at this URL:
http://www.youtube.com/watch?v=yhzMYHiuEC4.

MEDIA

Click image to the left for use the URL below.

URL: http://www.ck12.org/flx/render/embeddedobject/94342

Summary

• Pascal’s law states that a change in pressure at any point in an enclosed fluid is transmitted equally throughout
  the fluid.


• The ability of fluids to transmit pressure in this way can be very useful—from getting toothpaste out of a tube
  to applying the brakes on a car.