| When you look at large, powerful pieces of machinery, specifically construction equipment, you see that each is unique in its own purpose. But one feature that unites most of these machines is that they are powered by moving liquids! This technology is called hydraulics, and it's used to power everything from car brakes and garbage trucks to motorboat steering and garage jacks. We know that solids, liquids, and gases have very distinct physical properties and each obey their own laws of physics, but how does that play into the science of hydraulics? Let’s take a closer look! |  |
Imagine you have a block of wood in one hand, and a balloon in the other. It’s relatively easy to squeeze and pop the balloon, and you it’s pretty much impossible to squeeze a block of wood into another shape using your bare hands! Since liquids flow smoothly from place to place, you might think that they’d act more like a gas than a solid if you tried to “squash” a liquid. However, think about a time where you’ve jumped into the water and accidentally landed in a belly flop. When your body hits the water at such a high velocity, it hurts because liquids are virtually incompressible! Water can’t squeeze downwards (like a trampoline or mattress would) or move out of the way (like the air can) quickly enough to accommodate for the extra mass. That’s why jumping/diving incorrectly from a great height is so dangerous; it’s almost like jumping down onto concrete!
Let’s look at another example: why does water squirt out of a syringe like a water pistol if you depress the plunger? You can't really compress a liquid at all, so if you force the water up through the wide part of the syringe by pushing hard on the plunger at the bottom, where's that water going to go? It has to escape through the top. Since the top is much narrower than the bottom, the water emerges in a high-speed jet.
Hydraulics runs this process in reverse to produce lower speed but more force, which is used to power many machines. It's exactly the same in a water gun, which is essentially just a syringe shaped like a pistol. If water guns can change force and speed, that means they work just like tools and machines. In fact, the science of water pistols powers some of the world's biggest machines - cranes, lift trucks, and diggers!
The science behind hydraulics is called Pascal's principle. Put simply, because the liquid in a pipe is incompressible, the pressure must stay constant all the way through it, even when you're pushing it hard at one end or the other. Pressure is defined as the force acting per unit of area, so if we press down with a small force on a small area, at the narrow end of the tube on the left, there must be a large force acting upward on the larger area piston on the right to keep the pressure equal. That's how the force becomes magnified.
You can see hydraulics at work in this digger. When the driver pulls a handle, the digger's engine pumps fluid into the narrow pipes and cables (indicated by blue arrows), forcing the hydraulic rams (circled in red) to extend. The rams look a bit like bicycle pumps working in reverse. If you put several rams together, you can make a digger's arm extend and move much like a person's—only with far greater force. The hydraulic rams are effectively the digger's muscles!
You can even experiment with hydraulics yourself! Try making a hydraulic lifter like the one in this experiment using some tubing and a few household items. The pressure from the tube is enough to force water into the balloon. Filling the balloon can lift a tin can, which is strong enough to hold the weight of a book!
References:
“Hands-On Hydraulics: Science Fun for Kids.” Navigating by Joy, 29 September, 2013. http://www.navigatingbyjoy.com/2013/09/29/hands-on-hydraulics-science-fun-for-kids/
Image Credits:
Brennan, Paul. “Shipyard Crane”. Released into the public domain. Uploaded on 8/31/17 from publicdomainpictures.net
“Jumping Jack: Dog Jumping into Water”. Released into the public domain. Uploaded on 9/1/17 from publicdomainpictures.net
Stachowiak, Kai. “Syringe”. Released into the public domain. Uploaded on 9/1/17 from publicdomainpictures.net. Image modified by Erin Nyren.
Brennan, Paul. “Construction Site”. Released into the public domain. Uploaded on 9/1/17 from publicdomainpictures.net
You can even experiment with hydraulics yourself! Try making a hydraulic lifter like the one in this experiment using some tubing and a few household items. The pressure from the tube is enough to force water into the balloon. Filling the balloon can lift a tin can, which is strong enough to hold the weight of a book!
References:
“Hands-On Hydraulics: Science Fun for Kids.” Navigating by Joy, 29 September, 2013. http://www.navigatingbyjoy.com/2013/09/29/hands-on-hydraulics-science-fun-for-kids/
Image Credits:
Brennan, Paul. “Shipyard Crane”. Released into the public domain. Uploaded on 8/31/17 from publicdomainpictures.net
“Jumping Jack: Dog Jumping into Water”. Released into the public domain. Uploaded on 9/1/17 from publicdomainpictures.net
Stachowiak, Kai. “Syringe”. Released into the public domain. Uploaded on 9/1/17 from publicdomainpictures.net. Image modified by Erin Nyren.
Brennan, Paul. “Construction Site”. Released into the public domain. Uploaded on 9/1/17 from publicdomainpictures.net
