Past and Present
Machines
Machines
Machines with many parts that involve more than one simple machine are called
complex machines
A twist off jar lid is an example of this simple machine
screw
The point on which a lever rests and pivots on
fulcrum
Which has a higher mechanical advantage: fixed pulley or moveable pulley?
moveable pulley
If work remains the same and distance is decreased what happens to the force?
increases
Before vehicles were invented, people would travel long distances using this
horse and carriage
A ramp is an example of this simple machine
inclined plane
How effective a machine is at converting input energy to output energy
efficiency
A screw is a simple machine that is really a ________ wrapped around a cylinder
inclined plane
Another way to calculate mechanical advantage of a lever in addition to output force / input force is length of __________ / length of _________
effort arm
load arm
People used to fetch water from a well, using this simple machine to lower and raise a bucket
pulley
A zipper is an example of this simple machine
wedge
axis
Which simple machine is more efficient - inclined plane or pulley?
pulley
For a higher speed ratio, you would want a follower gear with more or less teeth?
less
This scientist said "give me a lever long enough and a fulcrum on which to place it, and I shall move the world"
Archimedes
A wheelbarrow is comprised of these two simple machines
lever and wheel and axle
The ratio of output force to input force in a mechanical system
mechanical advantage
This class of lever gives the most mechanical advantage
class 2
How do you find the mechanical advantage of a wheel and axle?
radius of wheel / radius of axle
Simple machines change the ________ and/or ________ of a force
direction
magnitude
A shovel is comprised of these two simple machines
lever and wedge
A group of two or more gears
Name 3 things a wedge can do
Cut, split, scrape, tighten and hold back, hold together
Which is more efficient:
1) a pulley system that has an output energy of 2J with an input energy of 10J
2) a lever that has an output energy of 2J with an input energy of 20J
1) a pulley system that has an output energy of 2J with an input energy of 10J