An enormously popular exhibit, this consists of a normal bicycle, a dynamo, and an attractive small "00" gauge electric train layout. When the bicycle is pedalled, (it does not move of course), the electricity generated by the dynamo drives the locomotive around the track, its speed varying with the speed of the bicycle wheel. Most children will first race the locomotive around the track, then will try and bring it to a halt at the station. The voltage generated is displayed on a meter, along with the current taken by the locomotive.
Note:The saddle is rather uncomfortable for adult bottoms, but the exhibit works fine if the pedals are operated by hand!.
The main part of this exhibit consists of two ramps, about 400mm high and 2metres long. One is wider than the other, but they are otherwise identical. Two identical pairs of wheels are provided, which are made to roll down the ramps. The pair of wheels on the wide ramp run on their tyres, those on the narrow ramp, on their axle. The user has to guess which pair of wheels will reach the bottom of the ramp first, or if there will be no difference. Most are surprised to find that the wheels running on their axle take perhaps ten times as long to reach the bottom. It makes no difference if the wheels are swapped to the other ramp. The reason? The wheels are accelerated by gravity - they can be considered to "take up energy" at a certain rate. The wheels running on their axle have greater inertia, and will take longer to accelerate. When these wheels reach the bottom of the ramp, however, they are spinning faster than the other pair, and will suddenly accelerate when their tyres contact the ground.
This is a 2 metre high acrylic tube, filled with water, and having a hand pump to increase the pressure of the air above the water. Inside the tube is a glass model of a deep-sea diver, which is normally floating. One or two strokes of the pump will send him to the bottom. He will rise again when the pressure is allowed to reduce. The changing level of the water inside the diver can be clearly seen. A fun demonstration of Archimedes Principle.
An earpiece, frequency control knob and a digital meter. The user listens to the beeps coming from the earpiece, and raises the frequency until they are no longer audible. This gives a fair measure of the upper frequency limit for that ear. Most people have different limits for their ears. This exhibit also measures your age - very young children can easily hear up to 20,000 Hz - older people may struggle to reach 10,000 Hz. This exhibit can be difficult to use if Discovery is very busy.
The user turns a contol to drive a small carriage across the exhibit, which consists of three bridges constructed from polyurethane placed between crossed polaroids. The three bridges have different stress characteristics, clearly shown as bands of colour when the wheels of the carriage press down on the polyurethane.