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
You might spot a bulldozer rumbling along an unpaved road as it moves dirt and gravel from the surface It may run on huge wheels but usually bulldozers move on caterpillar tracks These allow it to travel across soft ground without sinking because the wide tracks spread the machine’s weight over a larger area of ground A large metal plate called a blade sticks out on hydraulic arms at the front of the bulldozer It’s used to scrape off layers of soil and push them forward as the machine moves The driver manipulates the arms of the bulldozer from a cab that’s usually safely enclosed WORKING PARTS Which kind of machine helps the arm lift loads ACTION Bulldozer 6
A first-class lever such as a crowbar has the fulcrum in the middle The load and the effort are at either end A second-class lever has the fulcrum at one end the load in the middle and the effort at the other end A wheelbarrow is a second-class lever A lever is a bar or rod that moves around a support known as the fulcrum A force used to move one end of the lever will lift a load at the other end The closer the fulcrum is to the load the less effort is needed to lift it There are three different classes of lever depending on where the fulcrum is placed The ripper is a long claw-like device that’s located at the back of the bulldozer It’s used to tear up rock or hard earth into small pieces of rubble that are easier to remove Bulldozers are used on road sites and construction sites in mines and factories and even on military bases ANSWER THE LEVER A third-class lever has the fulcrum at one end the effort in the middle and the load at the other end Your arm is a third class lever and so is the lifting arm of a bulldozer Different muscles in the arm supply the effort effort fulcrum load (cid:2) (cid:2) 7
