3 3 Hoist Truck Pedicab Monorail Glossary Index Credits 36 38 40 42 44 46 48 pulley hoist combustion engine wheel and axle electromagnet Machines are used to do work Work in this case describes what takes place when a force moves something To do work machines need energy The energy that machines use may be electrical energy or chemical energy from fossil fuels such as gasoline or diesel Power is the rate at which work is done It is measured in watts or horsepower Power can be as little as the power from a bicycle rider’s legs or as much as the massive power of a huge road train But all machines need energy and power Let’s look at some of the brilliant action machines that help us do different kinds of jobs and the science that makes it possible
What is the name for the energy used by road trains 4 As the road train rumbles by you might wonder just how many trailers the rig can haul Some road trains pull two trailers while others may pull as many as four Road trains in Australia are restricted to certain highways They’re too big to make their way through crowded towns They haul mineral ores livestock and fuel among other things ACTION Road train
Road trains like this operate mainly in Australia and Canada ANSWER HORSEPOWER When scientists talk about power they mean the amount of work something is capable of doing in a certain time Work is measured in joules Power is how many joules of work are done in a given time Power for road vehicles can also be measured in horsepower One horsepower is equal to 745 7 joules per second A road train must have lots of horsepower to pull its load (cid:2) (cid:2) One horsepower is equal to 745 7 joules per second 5
