# Hands-On Hydraulics – Science Fun for Kids

This hands-on hydraulics experiment is a fun way to investigate the power of liquids.

We used hydraulic power to create a simple machine which our Lego mini figs – and all the family – had fun playing with.

Our hydraulic theme-park even inspired a movie!

A liquid under pressure can apply a lot of force and this can be used by machinery to do work. Using liquids like this is a branch of engineering called hydraulics.

Science Experiments for Kids

## Hydraulic Lifter Experiment

### What You Need

• short length of tubing
• balloon
• empty can
• tape
• empty plastic bottle
• funnel
• heavy book
• water
• scissors

### What you do

{I’ve added a steps 1 and 2 to the instructions given in Science Experiments for Kids, to give you the benefit of our mistakes.}

1. Stretch the balloon by blowing it up and letting the air out again.

2. Attach the tubing to the empty balloon and seal the join with tape. Check the join is water-tight by attaching the funnel to the other end of the tube and filling with water. Remove the funnel and drain out the water.

3. Cut the empty bottle so that it is just a little taller than the can. (We should have cut a bit more off ours.) Use a pencil to make a small hole near the bottom of the bottle.

4. Feed the free end of the pipe through the hole in the bottle, leaving the balloon inside.

5. Put the heavy book on top of the bottle.

6. Attach the funnel to the pipe and fill with water. (Hold the funnel up high to quickly release any air bubbles.)

### What happens

The water-filled balloon lifts the can, which in turn lifts the book.

The balloon feels very firm.

### The scientific explanation

The weight of the water in the funnel creates enough pressure to force water into the balloon. This force is in turn transmitted through the balloon to lift the book.

Fluids transmit forces more effectively than gases because they can’t be compressed, even under pressure.

## Hands-on hydraulics fun

We wanted to apply what we’d learned to create something like this very cool hydraulic elevator.

Unfortunately we couldn’t get our syringes and pipes sealed tightly enough to make it work.

Instead, C(9) had the idea of using hydraulic pressure to create a fun ride for Lego mini figures.

### Real life hydraulics

Liquids are used in many kinds of machines to carry force through pipes.

Most of us rely on hydraulic machines every day, for example when we apply the brakes in our cars or fill them with petrol, and even when we run the dishwasher.

Hydraulics is used to design piping systems, pumps, propellers, water turbines, hydraulic presses, and flow-measuring devices.

Britannica Online for Kids

We enjoyed dipping our toes into hydraulic principles.

There are lots more hydraulics experiments I hope we’ll do in the future. They’re a great hands-on way to learn about the laws of physics, such as Pascal’s Principle.

For more pressure science, see our air pressure experiments.

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# How to Make a Balloon Hovercraft

We’ve wanted to try a hovercraft experiment since we saw a really cool leaf blower hovercraft (like this one) at a science show last year. As we don’t have access to a leaf blower, we used balloon-power!

There are many variations on this experiment. We tried quite a few.  I’ll start with the one that worked best and then show you some of the others. (Maybe you’ll have better luck with them.)

### What you need

* old CD

* hot glue gun

* sports cap from a water bottle (the kind that you pull up to drink and push down to close)

* push pin (drawing pin)

* large balloon

* a big smooth surface

### What you do

1. Use the push pin to make two holes in the cap near the centre.

2. Spread a thin layer of hot glue around the base of the bottle cap and attach it to the CD, over the hole. Give the cap a slight twist as you stick it to ensure an airtight seal.

3. Make sure the cap is down (closed).

4. Blow up your balloon and pinch its neck while you attach it to the top part of the cap. (Easiest with two people.)

5. Place your hovercraft on a smooth flat surface. Give it a push and see what happens {not much}.

6. Now, without removing the balloon, pull up and open the cap. Quickly give the hovercraft a push and watch it continue moving. Push your hovercraft back and forth across a flat surface to keep it moving until the balloon is fully deflated.

Notes: (1) I’ve since seen the experiment set up this way in Science Experiments, but without the pushpin holes

(2) I’ve also seen a version that uses sticky tack (Blue Tack) instead of hot glue

### The scientific explanation

When you push the hovercraft when the cap is closed (stage 5 above) , friction between the CD and the surface soon stops it moving.

But when you open the cap, air escaping from the balloon cushions the hovercraft. The hovercraft continues moving much farther.

### Variations that didn’t work for us {but it’s good to experiment}

1. First we tried making Science Bob’s hovercraft. This involved taping over the CD hole and making six push pin holes in it. No holes were in the lid.

Verdict: A complete dud! I’m not sure what we did wrong, but this hovercraft didn’t do much for us.

2. The version that eventually worked for us was from Steve Spangler Science. But Steve Spangler suggests making a cardboard collar for the hovercraft.

Verdict: We made a collar and the hovercraft worked fine, but it was very fiddly trying to get everything attached and the cap open. We eventually removed the collar in frustration, and found that the hovercraft worked just as well without it.

3.  We tried making a hovercraft just using  a paper plate and balloon.

Verdict: Another dud! Perhaps we didn’t make our centre hole big enough?

### Hovercraft History

The first modern hovercraft was designed in the 1950’s by Englishman Sir Christopher Cockerel. It crossed the English Channel between Dover, England and Calais, France in two hours.

Until the year 2000, passengers could travel from England to France by hovercraft in just 35 minutes.  Passenger hovercrafts still operate between Southsea, England, and the Isle of Wight.

Hovercrafts are a type of seaplane, and they require large amounts of expensive aviation fuel to keep their giant air-cushions inflated. This is one of the reasons large hovercrafts are less commonly used nowadays.

#### Military Hovercrafts

Because hovercrafts are able to cross any flat terrain, including water, marshland, tarmac and sand, they are still commonly used for military purposes.

The biggest hovercraft in the world – the Zubr – recently made the news when it landed on a Russian beach filled with hundreds of sunbathers. A Russian defence spokesman reportedly commented, “What people were doing at the beach on the territory of a military base is unclear.” Okay, then!

#### Sources

History of the Hovercraft – Squidoo

Giant Hovercraft Retire after 30 Years of Channel Crossings

### Coming Up

Next time –  How to make a hydraulic lift

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