Skip to main content
Activity (Hands-On)Grades 6 - 8

Fluid Forces: Powering Bridges with Hydraulic Systems

A photo showing a bridge constructed from popsicle sticks, with a rectangular platform as the base and a rectangular platform as the top/bridge portion. The top platform is held up in each corner using 2 wide popsicle sticks glued vertically to form a corner. The front of the bridge has a wall between 2 corners that is holding one syringe and the plastic tubing. The second syringe is attached to the base using zip ties. When the syringe on the base is pressed, it causes the syringe attached to the front wall to push up vertically and raise the top platform. The platform is lowered by pulling the syringe attached to the bottom base.Student example of a hydraulic bridge

Students explore the science and engineering behind hydraulic bridges. They begin by considering how bridges lift to allow large ships to pass and learn that hydraulic systems use pressurized fluids to generate controlled, powerful motion. Through hands-on exploration with syringes filled with air, water, and viscous substances, students observe how different fluids transfer force and how viscosity affects movement. These investigations reinforce key physics concepts, including balanced and unbalanced forces, fluid behavior, and Newton’s First Law of Inertia. Students then apply this knowledge by designing and constructing a model hydraulic bridge using syringes, tubing, and craft materials. During the design process, they evaluate stability, force transfer, and structural support while troubleshooting and refining their ideas.

Engineers who create hydraulic bridges come from several specialties and work together to design structures that can safely lift, rotate, or open using powerful fluid-driven systems. Civil and structural engineers plan the overall bridge design, making sure it can support heavy loads and withstand environmental forces, while mechanical engineers develop the hydraulic components—such as pistons, pumps, and valves—that allow the bridge to move smoothly and reliably. Electrical and control systems engineers add sensors, wiring, and automated controls that coordinate the bridge’s motion and ensure safe operation. By combining their expertise, these engineers create bridges that are both strong and dynamic, allowing boats and vehicles to move efficiently through shared spaces.

After this activity, students should be able to:

  • Understand how balanced and unbalanced forces affect motion.
  • Understand how hydraulic systems work and how fluids behave under pressure.
  • Explore the structural components and mechanisms of famous hydraulic bridges.
  • Design, build, and test a hydraulic bridge prototype that meets specific criteria.
  • Collaborate effectively in teams to research, brainstorm, and execute a project.

More Like This