Alfred Payson Gage.

Physical technics; or, Teacher's manual of physical manipulation, etc online

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Enter^ &6cdrdinSr to 2Mt ofTObngiew, Uii^^year 1884, by

in the OflSce of the Librarian of CongreM, at Wasbington.


J. S. CusHiNG & Co., Printbrs, 115 High Strsbt, Bostok.

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XT has been our aim to collate in this volume something of
value to every teacher of Physical Science. For valuable
suggestions and aid in our efforts, we are deeply indebted to
Prof. W. LeConte Stevens of Packer Institute, Brooklyn, N.Y. ;
Prof. M. B. Crawford, Wesleyan University, Middletown, Conn.,
and Rev. J. G. Griffin of Ottawa College, Canada. Mr. Arthur
W. Goodspeed of Harvard University prepared the key to the
solution of problems. Messrs. J. S. Cushing & Co., Boston,
are entitled to the credit for the excellence of the typograpljy,
and Messrs. Berwick & Smith, Boston, for the presswork.



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Laboratory Exercises 1-84

Manual op Manipulations 85-129

PART in.
General Review of Physics 130-168

Test Questions 159-fr9

Key to Solution of Problems 180-200

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Part I.




Suppose that we have two quantities, x and y^ so Telated to
each other that any change in one alters the other ; for example,
let X represent the interest, compound or simple, for a term of
y years. Take a piece of engineer's paper, Fig. 1, divided into
squares by equidistant vertical
and horizontal lines. Select one
of each of these lines to start
from. The vertical line is called
the aons of F, and the horizontal
line the aods of X, and their
intersection the origin. Take
point a as the origin, and let
the horizontal spaces to the right
represent the number of years,
and the vertical spaces multiples
of the first year's interest ; then
points a'y a", a"', etc., represent
the interest at the end of the
first, second, third, etc., years.
Connect these points by a straight line aA» Now, if we take
any point, as c, in this line, and connect it with the axis T by
a horizontal line nc, and with the axis X by vertical line mc^
the former will represent the time and the latter the interest


























Fig. 1.

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r2; ••:-'•••:; : .xabTobatory exercises.
• •• -••" *•«»<# • •'

which has accrued at that time. The line nc is called the
abscissa^ and the line mc the ordinate of the point c. In a
similar manner are found points 6, 6', 6", etc., representing the
compound interest at the end of the second, third, and fourth
years. Having connected these points by the curved line aJ5,
the ordinate of any point in this line will represent the com-
pound interest which has accumulated at the time represented
by its abscissa. What does the point A represent? the point
5? the line AB'^

Experiment 1. Construct a number of curves representing
familiar phenomena, as the changes of temperature during the
day or year, barometric changes, the velocity of a falling body,
the declination of the magnetic needle at New York City (see
p. 83) from 1680 to 1880, volumes of a given amount of air
corresponding to different pressures, etc.


Exp. 2. Make saturated solutions of vttrious substances, such
as ammonium chloride, ammonium oxalate, potassium nitrate,
cuprum nitrate, potassium bichromate, ferrum sulphate, barium
chloride, urea dissolved in alcohol, etc., and flow slips of well-
cleaned glass with each of these solutions. Allow them to
dr^n for a few seconds, and then, with a microscope or common
magnifying glass, watch the growth of the crystals as they form
upon the glass.

Exp. 3. If the teacher possesses a porte-lumi^re, or a stere-
opticon, he should project the above on a screen by using the
wet slips of glass as he would use the ordinary stereopticon
slides. If the growth of crystals is slow, as is apt to be the
case when the liquids are not fully saturated, it will be well to
warm the slips of glass by waving them over a Bunsen or alcohol
lamp flame, and then pour the solutions upon the warm glass.

It would be well to encourage pupils to collect cabinets of
crystals. The cr3'stals should be preserved in small, well-stop-

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pered bottles or test-tubes. Single crystals may be mounted
on heads of pins, the points of the pins being thrust into cork
so as to hang from the same inside the bottles.

Exp. 4. Examine with a common magnifying glass a freshly
broken surface of cast iron, and observe the crystalline appear-
ance of the fracture.

Exp. 5. Make a cold saturated solution of table salt, and
allow it to stand several days. As the water evaporates, small
crystals of salt will be formed. Make drawings of crystals of
all the substances used,


Exp. 6. (By Sir Wm. Thomson.) Take a cake of shoe-
maker's wax, 18 inches in diameter and 3 inches thick, and
place it in a shallow cylindrical glass vessel. Below the cake
place a number of corks, and on top of the cake some lead
bullets. Fill the glass vessel with water to prevent great vari-
ations in temperature. In about a year's time the corks will
float up through the wax to the top, while the bullets sink to
the bottom, showing the viscous nature of the wax.

Exp. 7. Take a strip of sheet lead about 40^ long and 2*'"*
wide, and attach to one end by means of a clamp of some kind
a weight of about 300*. Support the whole in a vertical posi-
tion by means of another clamp applied to the upper extremity,
and note at regular intervals of time, by means of a fixed scale
placed beside it, the elongation which has taken place. ,Draw
curves of viscosity, the ordinates marking the elongation and
the abscissas the units of time.

Exp. 8. Determine the viscosity of glass. Get a glassblower
to make a coil about 6*^"" in diameter and 20*^™ long from a piece
of glass tubing about 1.5™ long and 6"™ in diameter. Suspend
the coil in a vertical position, and attach to the lower extremity
a weight of about 20*.

Exp. 9. Determine the viscosity of wires of different metals
wound into coils, and draw curves of viscosity for each.

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Exp. 10. Compare the solubilit}' in cold and in hot water of
alum, saltpeter, common table salt, white vitriol (zinc sulphate),
etc. In each case take 10*=* of cold water in a test-tube ;
pulverize the solid to be tested, weigh out 50* of it, place a
small quantity in the test-tube, cover the mouth with a finger,
shake well, and observe the rapidity with which it is dissolved.
Continue to add small quantities at a time (smaller as it ap-
proaches the saturated point), as long as it is dissolved; and,
when saturated, weigh the remaining solid. Its weight = a

grams. Then — ^^— = ic, the solubility of the given substance



in cold water.

Exp. 11. Next suspend the test-tube in boiling water, and
continue adding small quantities of the substance till saturated.


Weigh the remaining solid ; its weight = h. Then


= 2^5

the solubility of the given substance in water almost boiling.
Prepare blanks, and record your results as follows : —

Solubility in Water.


Almost Boiling.




The solubility of a substance is the weight in grams of the
solid which 1 gram (1*^*^ when water is used) of the solvent
requires to form a saturated solution. In stating the solubility
of a substance, ought the temperature of the solvent to be
given ? What weight of alum will 40*^" of cold water dissolve ?

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What weight will the same quantity of hot water dissolve ? How
does the solubility of alum in hot and cold water compare ?

Exp. 12. Ascertain approximately the solubility of the sub-
stances used in the last experiment in cold alcohol.

Exp. 13. Put a granule of gum mastic in a test-tube con-
taining water, and shake. Do the same with granules of iodine
and analine.

Exp. 14. Repeat the last experiment, using alcohol as a

Exp. 15. Pour the solution of mastic obtained in the last
experiment into a tumbler of water.

Exp. 16. To 4*^ of a concentrated solution of sodium sul-
phate add 2*« of alcohol. •

In which are organic substances — i.e., substances of animal
or vegetable origin — more commonly soluble, in water or in
organic solvents such as alcohol ? Can one liquid diminish the
solvent power of another?


Exp. 17. Take about I*'* of ammonia water in a test-tube, and
immerse the lower end of the tube in hot water; in about a
minute close the mouth of the tube with the thumb, invert it in
a vessel of cold water, and remove the thumb.

Exp. 18. Make a paste of plaster of Paris about 1*^ in depth.
Take a glass tube 20*^ long and 2*^ in diameter, and thrust one
end vertically into the paste, and hold it there until the paste
hardens. Allow the tube to stand for a day or more to allow
the excess of water in the plaster plug to evaporate. Hold the
tube vertically, with the plugged end upward, and introduce a
rubber tube connected with a gas jet, and fill with illuminating
gas. Thrust the open end just beneath the surface of water,
and hold it there for a few minutes. The water will gradually
rise in the tube in consequence of the osmose of the gases.

Exp. 19. Pour into a saucer about 5*^ of ether or bisulphide
of carbon, and notice the rapidity with which its vapor diffuses

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through the air in a room, its presence being recognized by the
sense of smell. The molecules issue from the bottle with great
velocity ; and, if their progress were not interrupted by striking
against the air particles, the room would be instantaneously
permeated by the odor.


Exp. 20. Prepare a concentrated solution of common salt, sul-
phate of soda, or sulphate of zinc. Introduce first into pure
water, then into the solution a wooden demonstration hydro-
meter like that described in § 64, Physics, and, noting the
depths to which it sinks in each liquid, calculate from the data
obtained the density of the solution. In doing this, the pupil
will intuitively grasp the philosophy of the hydrometer.

Exp. 21 . Place an ordinary heavy-liquid hydrometer in water ;
then add gradually (as fast as it will dissolve) powdered sul-
phate of soda, stirring with a glass rod, and note from time to
time the density of the liquid. Draw a curve of density repre-
senting the density by abscissas, and the number of grams of
solid dissolved by ordinates.

Exp. 22. Place a light-liquid hydrometer in cold water, then
in water at a temperature of about 80° C, and note the density
of ttie two waters. Why must the standard of specific gravity
be given at a definite temperature ?

Exp. 23. Measure the capacity of some small cavity. First
weigh the article containing the cavity, then weigh the same
with the cavity filled with mercury, divide the difference between
the two weights by the specific gravity of mercury, and the
quotient will be the capacit}^ in cubic centimeters.

Exp. 24. According to the principle of parallel forces, the two
arms of a balance beam ought to be precisely equal ; otherwise,
unequal weights will be required to produce equilibrium. Test
your laboratory balances by placing weights in the two pans
until the beam becomes horizontal. Then interchange the con-

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tents of the pans ; if the beam remains horizontal, the arms are
equal, otherwise it will descend on the side of the longer arm.

Exp. 25. Paradox, Take a strip of tin 50*^ in length and 6""
in width, and bend it into the form of a circular hoop ; solder
the two ends together. At some point in the interior of the
hoop solder a lump pf lead weighing about half a pound. This
hoop may now be placed upon an inclined plane in such a posi-
tion that it will apparently roll up hill.

. Exp. 26. Bore holes about 2"^ in diameter with the point of a
pen-knife blade in the opposite ends of a hen's egg ; blow the
contents out. Drop pulverized rosin through the hole in the
large end so as to cover the interior surface of the small end ;
then pour melted lead through the same hole, so as to " load "
the small end. In whatever way you place the shell, it will
stand on the small end.

Exp. 27. Take a long glass tube (the longer the better) , closed
at one end with a tight-fitting cork, fill it with water, and sus-
pend it in a vertical position by a light spiral spring from the
ceiling. Suspend at the top of the water column a number of
bullets attached to the tube by a thread. With a flame, buni the
thread ; during the descent of the bullets through the water, the
spring contracts and the tube rises.
Account for this phenomenon, and
make a practical application of the
principle involved. When any por-
tion of our atmosphere ascends, in
consequence of a denser portion de-
scending, how will the pressure of
the lower strata be affected ?

Exp. 28. Prepare a V-shaped bar p^g. 2.

like that shown in Fig. 2, the bar

AO being about 3 feet long ; place it so that the end will
overlap the table two or three inches, and hang a heavy weight
or a pail of water on the hook 5, and the whole will be sup-
ported. Eock the weight back and forth b}'^ raising the end O

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and allowing it to fall. What kind of equHibrium is this?
Remove the weight, and the bar falls to the floor. Why ?

Exp. 29. In the small end of an egg make a hole about 2"*"
in diameter, and place it, the small end downward, in a wine-
glass, so that the end of the egg will be within 1™" of the bottom
of the glass. Place the whole under the. receiver of an air-
pump, and exhaust the air. The air which is contained in a
small sack at the large end of the egg will expand and expel
some of the contents of the egg. But, on re-admission of air to
the receiver, the pressure of the air will drive the fluid back into
the shell.


Exp. 30. Insert the stopper a (Fig. 3) in the base, and
remove the caps 6, c, d, and e, and fill the cup /with water so
that the liquid surface will be above the bend ^, and the lateral
pressure of liquids will be shown by the issue of liquids from the
side orifices. (It may be necessai*y to remove temporarily the
cap from h to allow the air in the tube to escape.)

Exp. 31. That pressure increases with the depth is shown by
the increase of velocity of the streams as the depth increases.

Exp. 32. Remove the stopper a, and the liquid ceases to flow
from the side orifices, showing that during the free fall of liquids
there is no lateral pressure,

Exp. 33. Replace the stopper a, and the caps on 6, c, d, and
e, and remove the cap from ^, and connect with this tube, by
means of a rubber connector, a glass tube i ; and, elevating the
latter at various angles, the exact paths of projectiles at these
angles are shown.

Exp. 34. Remove the stopper a and the cap from j^ and
close all the other orifices ; connect with the tube j a glass tube
A:, the lower end of which dips into a vessel of liquid m, and
this liquid will be drawn up the tube, illustrating the action of
the Sprengel pump.

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Exp. 35. It will be seen that the receiver / is a Tantalus <iup^
and that here it is turned to a practical use, inasmuch as it will
not suffer the liquid to flow until the vessel is full, and all is
ready for the experiment.

Exp. 36. It is evident that, when the cap
is removed from A, and the tube i is suitably
elevated, the instrument becomes a sipJion-

Exp. 37. The fountain may easily be
made to represent an intermittent spring or
fountain b}^ placing above the receiver a
large vessel of water n, from which liquid is
siphoned into the receiver /. The siphon
delivery being smaller than that of the Tan-
talus tube, it is evident that the fountain
will operate intermittently and at regular
periods, inasmuch as the liquid will not flow
from the Tantalus cup until it is filled to the
level of the bend, and will then flow until
the cup is empty.

Exp. 38. Place the apparatus from 8 to
12 ft. above the ground, remove the caps
6, c, d, and e, fill the cup /with water, and
note the maximum horizontal distance,
measured on the ground, which each stream
attains. Draw a curve of pressure, the ordi-
nates representing the distance of each ori-
fice below the bend ^, and the abscissas the
horizontal distances attained respectively by
the streams. Draw a curve of velocity on
the principle that the velocity varies as the
square root of the pressure or head of water,
the ordinates representing the velocity and
the abscissas the pressure at the several
orifices. ^«' ^'

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Exp. 39. Stop up all the orifices but one, and note the num-
ber of seconds it takes to empty the cup through that orifice ;
do the same with each orifice, and draw a time curve represent-
ing the time by ordinates and the distance below the bend g by

Exp. 40. Provide glass tubes 20^, 40«», 60«", and 80"» long,
and of uniform bore ; connect them successively with the tube i^,
and note the time consumed in emptying the cup through each.
Draw a curve of hydraulic friction^ the abscissas representing
the increment in length of tube, and the ordinates the increment
in time consumed, or friction.

Exp. 41. Keep the cup constantly full by pouring or siphon-
ing water into it. Close all the orifices save one, the stream
from which you wish to represent graphically. Determine the
horizontal projection or random of suitable points of the
stream by measuring perpendicularly from a line let fall from
the orifice ; also determine the vertical distance of each point
below the orifice ; then, by means of corresponding ordinates
and abscissas, and on a scale of equal parts, construct a
graphical representation of the stream. In similar method
represent the paths of the streams from the several orifices.

Exp. 42. Connect the glass tube i with A, elevate it to any
desired angle, fix it firmly in this position, and make measure-
ments similar to those in the last experiment, except that the
vertical distances are to be measured upward from the orifice
h ; construct from the data obtained a graphical representation
of the path of a projectile directed at this angle. It will be
found convenient to make all the horizontal measurements
from the vertical tube ag, deducting therefrom the length of
the horizontal tube.

Exp. 43. Elevate the tube i so that it will be nearly vertical,
and observe how much the stream falls short of reaching the
orifice of the tube in the cup when the bend g is covered.
If the stream encountered no resistances from the air, or
from friction against the sides of the tube, how high ought

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it to rise ? If to the velocity of efflux from the orifice h there
should be added the velocity which is lost in consequence of
resistances, how would the sum compare with the velocity
which a stone would acquire in falling a distance equal to that
from the surface of water in the cup to the tube h ?


Exp. 44. Suspend the instrument, Fig. 4, from some con-
venient support, and rarefy the air within it by suction with
the mouth; a weight of 20 lbs. ought to be easily raised.
This weight, added to a probable friction of about 15 lbs.,
gives 35 lbs. as the unbalanced pressure exerted by the outside
air on the piston.

Fig. 4. Fig. 5.

Exp. 45. Push the piston quite into the cylinder, and close
the stop-cock, and let a person grasp each of the handles
and attempt to pull the piston out. It is apparent that in
his attempt he creates a vacuum, and few will be found
strong enough to draw the piston out. This constitutes a most
interesting modification of the classical Magdeburg Hemispheres^
but with this important advantage, that it produces a self -cre-
ated vacuum (the harder the pull the higher the vacuum) , and
requires no air-pump.

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Exp. 46. Let a person alternately blow and suck air through
the rubber tube (Fig. 5), and he will find it difiScult to resist
the forces (what forces?) tending to move the piston.

Exp. 47. Does the weight which is raised correctly represent
the lung-power exerted, or is it a case similar to that in which

a force is applied to the long

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Online LibraryAlfred Payson GagePhysical technics; or, Teacher's manual of physical manipulation, etc → online text (page 1 of 15)