Julius Sumner Miller: Lesson 15 - Levers, Inclines Planes, Geared-wheels and Other Machines
12.1 هزار بار بازدید -
11 سال پیش
-
All the machines in the
All the machines in the whole world - however complicated - are made up of combinations of the so-called SIMPLE MACHINES: The lever - the wheel and axle - the pulley - the inclined plane - the wedge - the screw. These can be further reduced to TWO: The lever and the inclined plane. All about us there are abundant illustrations of these wonderful devices:
A - The ordinary fork-and-knife at dinner: The knife is a lever AND an inclined plane! Why? When held in the hand it is used as a lever; the edge is sharp - and this is an inclined plane! The tines of the fork are also sharpened which makes them inclined planes! OK?
B - The screw-driver is a lever: We grasp the handle and twist. The
lever-arm is the radius of the handle. So it is really a lever. And a bigger screw-driver provides a bigger lever-arm!
C - The screw-thread is an inclined plane: If we wrap an inclined plane around a cylinder we get a "threaded screw" .
D - Wrenches are levers and Stillson wrenches are useful in the opening of screw-1 ids on bottles.
E - The ordinary kitchen grater is an array of inclined planes. The sharpened edges make them so.
F - A railroad spike is an inclined plane. So is a pointed nail.
G - The ordinary claw-hammer is obviously a lever. We increase the
mechanical advantage by using a block under the head as we pull a nail. AND NOTE WELL: The nail gets hot when we drive it IN and when we pull it OUT.
H - The nutcracker is a lever. The broom is a -lever. Indeed - as we show -the broom can be used as a lever of two different classes.
I - Metal shears are both levers and inclined planes.
J - A metal file - and a lady's nail file - are inclined planes.
K - A meat grinder is a compound machine - it consists of a lever and a screw. And the screw is an inclined plane.
And so we find these commonplace things possessing abundant enchantment when we explore them more thoroughly.
L - PULLEYS: The mechanical advantage of a pulley system is often calculates by counting the number of ropes supporting the load. This MAY give the right answer but it is NOT a reliable method. The point I wish to make here is this: We can.sometimes get the right answer by physically wrong means! This is bad.
We conclude this series of 15 programs with some large-scale philosophy: My ambition is NOT TO TEACH PHYSICS in these lessons - NOT TO POSE EXERCISES - NOT TO GIVE A COURSE IN PHYSICS. My singular ambition is to point up the Beauty and Drama in these Things - to stir your Curiosity -to awaken your Imagination - TO SEE HOW NATURE BEHAVES. Having always a watchful eye to THINGS ALL AROUND US and INCESSANTLY ASKING QUESTIONS will give a Fullness to Life and become a Stirring Adventure.
A - The ordinary fork-and-knife at dinner: The knife is a lever AND an inclined plane! Why? When held in the hand it is used as a lever; the edge is sharp - and this is an inclined plane! The tines of the fork are also sharpened which makes them inclined planes! OK?
B - The screw-driver is a lever: We grasp the handle and twist. The
lever-arm is the radius of the handle. So it is really a lever. And a bigger screw-driver provides a bigger lever-arm!
C - The screw-thread is an inclined plane: If we wrap an inclined plane around a cylinder we get a "threaded screw" .
D - Wrenches are levers and Stillson wrenches are useful in the opening of screw-1 ids on bottles.
E - The ordinary kitchen grater is an array of inclined planes. The sharpened edges make them so.
F - A railroad spike is an inclined plane. So is a pointed nail.
G - The ordinary claw-hammer is obviously a lever. We increase the
mechanical advantage by using a block under the head as we pull a nail. AND NOTE WELL: The nail gets hot when we drive it IN and when we pull it OUT.
H - The nutcracker is a lever. The broom is a -lever. Indeed - as we show -the broom can be used as a lever of two different classes.
I - Metal shears are both levers and inclined planes.
J - A metal file - and a lady's nail file - are inclined planes.
K - A meat grinder is a compound machine - it consists of a lever and a screw. And the screw is an inclined plane.
And so we find these commonplace things possessing abundant enchantment when we explore them more thoroughly.
L - PULLEYS: The mechanical advantage of a pulley system is often calculates by counting the number of ropes supporting the load. This MAY give the right answer but it is NOT a reliable method. The point I wish to make here is this: We can.sometimes get the right answer by physically wrong means! This is bad.
We conclude this series of 15 programs with some large-scale philosophy: My ambition is NOT TO TEACH PHYSICS in these lessons - NOT TO POSE EXERCISES - NOT TO GIVE A COURSE IN PHYSICS. My singular ambition is to point up the Beauty and Drama in these Things - to stir your Curiosity -to awaken your Imagination - TO SEE HOW NATURE BEHAVES. Having always a watchful eye to THINGS ALL AROUND US and INCESSANTLY ASKING QUESTIONS will give a Fullness to Life and become a Stirring Adventure.
11 سال پیش
در تاریخ 1392/04/29 منتشر شده
است.
12,195
بـار بازدید شده