Transcript Simple Machine-Law of Machine

Simple Machine-Law of Machine
► EN
NO. 130610106051EN NO. 130610106055
GUIDED BY
PROF. V.R.SHARMA
GEC PALANPUR
APPLIED MECHANICS DEPARTMENT
Machines
►A
device that makes work easier.
► A machine can change the size, the
direction, or the distance over which a force
acts.
What is Machine ?
A simple machine has
few or no moving parts.
Simple machines make
work easier
Simple Machine
► Simple
machine is a device in which effort is
applied at one place and work is done at
some other place.
► Simple machine are run manually, not by
electric power.
► e.g.
-pulley
-Wheel and axel
-simple screw jack, etc.
Simple Machine
► Simple
Machines
can be put together
in different ways to
make complex
machinery
Law of machine
For a particular machine, if we record various values of
effort
required to lift the corresponding load, we
shall get a straight
Mathematically,
Where,
P=mW + C
P=effort applied
W=load lifted
m=constant (coefficient of friction)
C=constant (machine of friction)
Pulleys
► Pulley
are wheels and
axles with a groove
around the outside
► A pulley needs a rope,
chain or belt around
the groove to make it
do work
Simple Pulley
Diagrams of Pulleys
Fixed pulley:
Movable Pulley:
A fixed pulley changes the
direction of a force;
however, it does not create
a mechanical advantage.
The mechanical advantage
of a moveable pulley is
equal to the number of
ropes that support the
moveable pulley.
Simple Wheel and Axle
wheel
►The
axle
axle is stuck
rigidly to a large wheel.
Fan blades are attached
to the wheel. When the
axel turns, the fan
blades spin.
Different Wheel and Axle and
Their velocity ratio
►
Velocity ratio (VR) = distance moved by effort
_________________________________________________________________________
distance moved by load
Screw
A screw is an inclined plane wrapped around a shaft or cylinder.
The inclined plane allows the screw to move itself when rotated.
The mechanical advantage of an screw can be
calculated by dividing the circumference by the pitch of
the screw.
Pitch equals 1/ number of turns per inch.
Screws
► Screw:
an inclined plane wrapped around a
cylinder
threads
Which screw would be easier to put into
a piece of wood?
-A screw with the threads very close
together or a screw with the threads
somewhat far apart
-The screw with threads CLOSE
together!
-Though it would take you less turns for
the screw with fewer threads, it would
require you to exert a greater force
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