According to NASA, a rocket engine works by burning fuel and pushing the resulting hot gas out through an exhaust nozzle on the rear of the craft. Since every action has an equal and opposite reaction, as stated by Newton's third law, the force created by the escaping gases pushes the rocket forward, even in the vacuum of space.Know More
Rockets may use either liquid or solid fuel. There are many different types of rocket fuel, but they all have reactivity in common. When the fuel is mixed or ignited, it produces large volumes of gas, suitable for propelling the vehicle forward. Petroleum-based fuels were used in early rocketry experiments, but these fuels work best in an atmosphere. Cryogenic fuels, like liquid hydrogen and oxygen, were used in the Space Shuttle and had the advantage of being extremely efficient. However, the need to keep the fuels supercooled prevented their use in rockets that may need to stand for long periods of time.
Hypergolic fuels, like hydrazine, require no ignition source, reacting and producing thrust whenever the components of the fuel mixture come in contact with one another. The fuels used in the Apollo spacecraft were hypergolic to ensure there could be no ignition problems once the spacecraft reached the moon.Learn more in Motion & Mechanics
Nuclear submarines are powered by a nuclear reactor located in the rear of the submarine. The nuclear reactor works similarly to a steam engine by heating water into steam. The reactor produces energy in the form of gamma radiation and heat by using a neutron to split an atom of uranium.Full Answer >
Moving water that flows through the porous rock of an aquifer is filtered by the tiny pore spaces in the rock. The pore size determines the size of the particulate matter that flows through; smaller pore sizes are helpful for filtering bacteria and other solid matter. Clay particles and other minerals slow down or stop dissolved substances so they don't travel with the water, providing another layer of filtration.Full Answer >
A machine is any device that transmits mechanical energy or power into useful work. The simplest machines redirect an applied force or convert kinetic energy into potential energy. More complicated machines are powered by electricity or fuel and use moving parts and electronic circuitry to complete complex tasks.Full Answer >
HowStuffWorks explains that levers work by reducing the force needed to move weights. They achieve this by increasing the distance through which the required force acts. For instance, a 1-kilogram force that acts through a distance of 3 meters is capable of moving a 3-kilogram weight in 1 meter, if friction is ignored.Full Answer >