1. A mix of water and alcohol.
   A mix of oil and gasoline.
2. Avtur.
   Diesel fuel.

Because two-stroke engines are a simpler design, the oil must be mixed in with the fuel to lubricate the parts. The power-to-weight ratio in a two-stroke engine is often much higher. Two-stroke engines tend to be less efficient but lighter.

1. A weed eater.
   An outboard motor.
2. High-octane gasoline.
   Diesel fuel.

Outboard motors are for propelling boats through the water. They use the water to cool them instead of air.

1. It is the order in which the furnaces in a coal power plant are started after maintenance.
   It is a complex formula that enables you to determine whether or not a car engine will misfire.
2. It is the order in which a spark plug ignites each cylinder in an engine block.
   It is the order the wheels on a train start moving.

The firing order of an internal combustion engine gives the order each cylinder is sparked to ignite the fuel. It is created to reduce lost power through vibration and other engine shifting.

1. The engine on a miter saw.
   The engine on a kitchen blender.
2. The engine on a steam engine.
   The engine on a computer disk drive.

The steam engine operates on combustion, not electricity. All of the others use small electric motors to convert electricity into mechanical power.

1. A jet engine.
   A marine engine.
2. A rocket engine.
   A two-stroke engine.

Rocket engines are internal combustion engines that work by expelling a gas that is the result of high-pressure combustion of propellants. The propellants must contain a fuel and the oxidizer (or grain) for that fuel.

1. A windmill.
   A jet engine.
2. An oil jack.
   A generator.

A jet engine is also known as a gas turbine engine. As gas is burned, it creates an air flow that spins turbines to create thrust.

1. To power an average car.
   To power a dirt bike.
2. To power a chainsaw.
   To power a lawnmower.

Although highly efficient, two-stroke engines burn a lot of oil. In addition to paying for gas, you would need to purchase about a half-gallon of two-stroke oil for every tank of fuel.

1. Powering a train with steam.
   Powering a submarine with heated air.
2. Creating electricity in a coal power plant.
   Using diesel to power a car.

A diesel engine ignites the fluid inside the engine. Coal power plants, trains, and submarines are all heating the air or water outside of the engine to drive the piston.

1. To reduce pollution.
   To increase thrust.
2. To decrease drag.
   To increase lift.

Afterburners are generally equipped on military aircraft to increase thrust during combat situations, takeoff, and supersonic flight. They work by introducing additional fuel into the pipe after the turbines. Afterburners are only meant to be operated for short periods of time because they consume large amounts of fuel.

1. The compressed gas is ignited, pushing the piston downward.
   The piston moves upward and pushes the gas into the exhaust system.
2. The piston moves upward and compacts the gas.
   The piston moves downward and pushes the gas into the exhaust system.

During the power phase in a four-stroke internal combustion engine, the piston moves downward after the gas in the chamber is ignited. The explosion creates the power that drives the piston through the rest of the cycle.

1. They create more pollution.
   They are extremely complex.
2. They are thermally inefficient.
   They are much heavier than four-stroke engines.

The main disadvantage that two-stroke engines have is that they burn the oil mixed in with their fuel, which increases pollution. They are simpler, lighter, and more efficient than four-stroke engines.

1. A radial engine.
   A rotary engine.
2. A chemical rocket engine.
   A turbojet.

Although all internal combustion engines contain combustion chambers, turbines are unique to the turbojet. Jet engines pass air or water in the opposite direction of the desired motion using Newton's third law of motion.

1. Rankine.
   Diesel.
2. Wankel.
   Radial.

The center of the Wankel engine (or rotor) rotates around a stationary gear inside the housing. The rotor is continuously moving in the same direction and driving the stationary gear forward.

1. A machine that changes mechanical energy into chemical energy.
   A machine that uses fuel.
2. A machine that changes heat energy into mechanical motion.
   A machine that turns a crankshaft.

An engine is a machine that converts energy, such as heat energy, into mechanical motion. The concept of an engine was first proposed in the 17th century.

1. To recharge the batteries.
   To power low, continuous speeds.
2. To aid in fast acceleration.
   A and C.

The gas engine in a hybrid car not only recharges the batteries but also improves acceleration and kicks in for higher speeds. The electric motor operates alone during lower speeds and slow acceleration.

1. A train steam engine.
   A hybrid car.
2. A jet airplane.
   A modern farm tractor.

External combustion engines use heat to power the piston, but the fire does not have direct contact with the piston. Steam engines are one example of this.

1. Steam.
   Fire or explosions.
2. Electricity.
   Turbines.

External combustion engines use a working fluid, such as steam, to move the piston. The heat source is outside of the engine.

1. A steamroller.
   An airplane,
2. A paddle boat.
   A passenger van.

The first successful rotary engine was designed in 1908. The design of the rotary engine aids in spinning propeller blades.

1. Electro-magnets.
   Hybrids.
2. Motors.
   Pumps.

By definition, "engine" and "motor" both are used as machines that power other devices. However, "motor" is generally used when the power comes from electricity instead of combustion.

1. Turbo-electric.
   Biomass-electric.
2. Petroleum-electric.
   Diesel-electric.

Although biomass is used to generate electricity, as of yet there are no biomass-electric hybrids in mass production. Turbines, petroleum, and diesel are all used in currently produced hybrid engine systems.

1. Diesel.
   Radial.
2. Stirling.
   Rocket.

All of the types except the Stirling are internal combustion engines. Diesel engines do not use spark plugs. Rocket engines are specialized jet engines. Radial engines are used to rotate the propellers in airplanes.

1. Reciprocating, uniflow, turbine, and oscillating.
   Reed inlet, rotary inlet, piston-controlled inlet, and uniflow-scavenged.
2. I, V, W, and U.
   Griffin, Dyer, Velozeta, and Beare head.

Although different oil delivery systems can cause variation between two-stroke engines, the main differences are based upon the gas inlet systems. Piston-controlled is the standard engine that uses the piston to control the intake.

1. Richard Trevithick.
   Robert Fulton.
2. Caleb Willow.
   Thomas Newcomen.

Robert Fulton was fascinated with steam engines and used one to power the first successful submarine, called the Nautilus, in the late 18th century. He went on to develop steam-powered torpedoes for Britain.

1. The Sterling engine.
   The Naptha engine.
2. The Organic Rankine engine.
   The high-pressure steam engine.

Robert Sterling invented the Stirling engine in 1816. It was an external combustion engine that used air instead of steam to move its pistons. The Sterling engine was safer (although prone to higher failure rates) and more efficient than steam engines of that era.

1. A jet engine.
   A six-stroke engine.
2. A radial engine.
   A Wankel engine.

The radial configuration is generally five pistons radiating out from a central point (the crankshaft). When viewed from the front, it resembles a star of sorts, and that is how it got its name.

1. To prevent the exhaust from escaping with the propellant.
   To direct the propellant into the combustion chamber.
2. To direct the spark into the combustion chamber.
   To accelerate the gas exhaust.

Nozzles on rocket engines allow the hot gasses to escape but accelerate the speed of the exhaust. Half of a rocket's thrust comes from the pressure created by the nozzle.

1. Magnetic.
   Piezoelectric.
2. HAWT.
   Electrostatic.

Magnetic motors are used the most. Electrostatic motors operate based on electrical charge attraction and repulsion, and piezoelectric motors are based on the principals of electric charge that accumulate in certain materials and vibration frequencies. HAWT (Horizontal Axis Wind Turbine) is a wind turbine not an electric motor.

1. An automobile.
   A train.
2. A vacuum.
   A boat.

The Stanley Motor Carriage Company produced steam vehicles in the early 20th century. It was founded by twins, Francis E. Stanley and Freelan O. Stanley. Francis died in 1918 in an automobile accident while trying to avoid two farm wagons and the company was sold.

1. It is cylindrical.
   It is a perfect sphere.
2. It is similar to a Reuleaux triangle.
   It is an ellipsoid.

The Reuleaux triangle is based on an equilateral triangle with bulging sides that create a constant curve. The Wankel engine uses sides that are slightly flatter than an official Reuleaux triangle.

1. The Rankine cycle is used to describe a spark engine, and the Otto cycle is used to describe a fluid that changes phases.
   The Rankine cycle is the ideal for external combustion engines, and the Otto cycle is the ideal for spark-ignition engines.
2. The Rankine cycle is used to describe low mass fluids, and the Otto cycle is used to describe high mass fluids.
   The Rankine cycle is the ideal for spark-ignition engines, and the Otto cycle is the ideal for gas-turbine engines.

The Otto cycle is used to ideally describe a situation where the working gas remains a gas constantly such as in spark-ignition systems. The Rankine cycle is the ideal in situations where the working fluid changes between gas and liquid states.

1. Radial engines have a rotating crankshaft; the crankshaft of rotary engines is fixed.
   Radial engines do not overheat as easily as rotary engines.
2. Radial engines were only useful until the 1920s, when drag limited power output.
   The radial engine has the pistons facing the central point; they point outward on a rotary engine.

A rotary engine rotates around a central, fixed shaft. It is for this reason Wankel engines are also called rotary engines, even though this term traditionally was applied to engines that spin, or rotate, with an airplane propeller.

1. Solid rocket.
   Cold gas thruster.
2. Turborocket.
   Hybrid rocket.

Cold gas thrusters operate like a balloon with the air being released. They provide low performance but can be useful for making minor adjustments to a space shuttle's course.

1. It is heavier than a piston engine.
   It is more expensive to mass produce.
2. Poor fuel economy.
   It is three times as large as a piston engine with an equal output.

Although running the engine at a constant speed overcomes fuel consumption issues, under normal operating conditions it consumes more fuel than what should be ideal. Linked to its poor fuel economy is also poor emission quality.

1. Trains.
   Bicycles.
2. Commercial airplanes.
   Personal watercraft.

After several boiler accidents on steamboats, laws were enacted that required an engineer to be present on all steamboats. The Naptha engine, although equally dangerous, was developed so the owners of personal watercraft could get around this law.

1. The Oruktor Amphibolos.
   The Model A.
2. The Steam Velocipede.
   The Puffing Devil.

The Puffing Devil was invented by Richard Trevithick in 1801. The first one was left unattended and running by its operators, and it self-destructed. By 1803, Trevithick had improved his design, but the London Steam Carriage never became popular.