Topic 6: Combining Systems Mechanical Systems Topic 6: Combining Systems

http://www.youtube.com/watch?v=_ve4M4UsJQo

A lever, pulley, and wheel and axle are examples of simple machines. Most modern machines are combinations of many simple machines, sometimes dozens or even hundreds of simple machines. They all work together to carry out a precise function.

As time passed, people expected more and more difficult tasks to be completed by machines. Machines became more complex.  Several simple machines all working together in a system are called complex machines.  A system is a group of parts that work together to perform a function. 

When a machine is part of a large system we call it a subsystem. A subsystem is a secondary or subordinate system that is part of a larger system. The braking system shown in fig 4.25B pg 326 is known as disc brakes.

The brake pedal subsystem is a class 2 lever. The force of the drivers foot on the pedal is the effort force. The load is the force on the piston that applies pressure on the brake fluid in the master cylinder. As the driver pushes down harder on the brake pedal, the effort force increases the pressure transmitted to the brake fluid. From the master cylinder, brake fluid flows through tubes that branch out to every wheel.

The brake fluid exerts pressure on the brake pads that press on the disc. The friction between the brake pads and the disc slows and eventually stops the car. The backhoe is a highly efficient combination of levers and hydraulics. It has 3 levers, a boom, a dipper, and a bucket

The boom is a class 3 lever that lowers and raises the dipper. The dipper is a class 1 lever that moves the bucket in and out. The bucket is a class 1 lever that is used to dig.

Another Rube Goldberg http://www.youtube.com/watch?v=qybUFnY7Y8w&featur e=kp