Vehicles use engines of different kinds to move people and
cargo from place to place. Most cars and motorbikes have petrol engines, but
vans and trucks use larger diesel engines. A diesel engine produces more power
than a petrol engine by compressing the air and fuel much more. Petrol and
diesel engines produce large amounts of pollution. ELECTRIC CARS
are less polluting.
Trucks have big diesel engines that produce more power than a car
engine, but they also use more fuel and produce more pollution. A truck is
heavier and moves with more momentum (force) than a car travelling at the same
speed. This is why a truck needs much more powerful brakes than a car and takes
a longer distance to come to a stop.
Electric cars use batteries or fuel cells instead of
engines and petrol. Batteries have to be charged up every so often, from the
mains or from an engine, and the car then runs until the batteries are flat.
Fuel cells work in a different way. Like an engine, a fuel cell takes in a
steady supply of fuel, usually hydrogen gas. Like a battery, it produces a
constant stream of electricity that powers an electric motor.
The world’s fastest solar-powered car, Nuna II, has a top
speed of 160 kph (100 mph). It is built in plastic and covered in solar panels.
These convert the Sun’s energy into electricity and store it in
batteries, so the car can also drive in the shade. The body, solar panels, and
batteries were originally developed for spacecraft.
HYBRID PETROL/ELECTRIC CAR
Petrol engines are good for driving at constant, higher speeds on
open roads. Electric motors are good for stop-start driving in city centres.
They have lower top speeds than petrol engines. Hybrid cars have both a petrol
engine and an electric motor. The car automatically switches between the two to
suit varying traffic conditions.
