7-1: Why We Use Machines
- A machine makes work easier by changing the size of
the force applied to it, the direction of that force, or both.
- The number of times a machine multiplies the force
applied to it is the mechanical advantage of the machine.
7-2: The Simple Machines
- A lever is a bar that is free to pivot about a fixed
point called a fulcrum.
- A pulley is a grooved wheel with a rope running along
the groove.
- A wheel and axle consists of two different-size wheels
that rotate together.
- An inclined plane is a sloping surface used to raise
objects.
- The screw and wedge are special types of inclined planes.
- Each type of simple machine has a specific equation
for calculating its ideal mechanical advantage.
- Each equation is related to the distance the effort
force moves divided by the distance the resistance force moves.
7-3: Mending with Machines
- The science of bionics tries to create artificial replacements
for parts of the body that are not functioning properly.
- Electronic stimulation can be used to move paralyzed
muscles or provide sensations for prosthetic limbs.
7-4: Using Machines
- A combination of two or more simple machines is called
a compound machine.
- The efficiency of any machine is a ratio of the useful
work put out by the machine to the work put into the machine.
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