102
1
input force
: what we put in
2
source
:
where something starts or
comes from
3
receptor
:
something that receives
4
output
:
the power or energy supplied
by a device
1.
WHAT IS A MECHANISM?
The moving parts of a bicycle are examples of everyday mechanisms that make life
easier and more enjoyable:
❚❚
The chain of a bicycle transfers motion to the back wheel.
❚❚
The bar of a seesaw forms a lever that we can use for fun.
❚❚
The gears inside old-fashioned clocks let us measure time
❚❚
The pulley system above a well helps us to bring up water.
Although these mechanisms are quite different, they all have something in
common. They make work easier because they
transmit
and
transform force
and motion
.
All of these mechanisms require an input
1
force and motion from some type
of source. In the case of a bicycle, our leg muscles are the input source
2
.
For other mechanisms, the input source might be an animal, an electric
motor, the force of running water, or the movement of weights, in the case
of an antique clock.
Mechanisms transmit motion and force to receptors
3
that finally perform the
work.
This is the output
4
force and motion. In the case of an analogue clock, the
output receptors are the hands of the clock that move in circles to show the
time.
1.1.
The parts of a mechanism
When you ride a bicycle, your legs provide the force and motion. The pedal
mechanism transmits input motion to the chain. The chain transmits the motion
to the back wheel, which is the output receptor. The wheel does work by moving
the bicycle forward.
ê
ê
Input of force
and motion
Mechanism
Output force
and motion
In the case of a bike, the small up-and-down motion of our legs transforms into a long
linear movement of our whole body.
Mechanisms
transmit and transform force and motion from an
input
source
(motor) to an output receptor. This transmission and transformation
lets us perform different types of work with more comfort and less effort.
Some mechanisms: bicycle,
seesaw,clock, well
ADVANCE EDITION
