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284 MECHANICS.
Body Projected in a Horizontal Direction From an
Elevated Place.
When a body is projected in a horizontal direction from a
place which is higher than the one where it strikes the ground,
the range in feet in a horizontal direction will be equal to the
product of velocity in feet per second and the time in seconds
which it will take for a body in a free fall to drop a distance
equal to the difference in vertical height between the two
places. Thus
:
Horizontal range = v A/ —
* S
v = Initial velocity in feet per second.
h = Vertical height in feet.
jr= Acceleration of gravity = 32.2 feet.
Example.
Water spouts from a nozzle in a horizontal direction at a
velocity of 30 feet per second and the nozzle is placed 12 feet
above the ground. What is the horizontal range of the water ?
Solution
:
Horizontal range = v -\j— = 30
\J-
X ,
2
= 22.45 feet.
To Calculate the Speed of a Bursted Fly=Wheel from
the Distance the Fragments are Thrown.
The angle of 45 degrees is the one most favorable to the
range ; therefore, suppose the fragments to leave the wheel at
that angle and use the formula,
v2
,
Horizontal distance = b = —— which transposes to v = a^/ fr
g
Rule.
Multiply the horizontal distance by 32.2, and the square root
of the product is the slowest possible rim-speed the wheel could
have had at the time of the accident.
Example.
A 30-foot fly-wheel bursts from the stress due to centri-
fugal force, and fragments were thrown a distance of 300 feet
from the place of accident. What was the slowest possible
speed the wheel could have had at the time the accident
occurred ? and what was the corresponding number of revolu-
tions per minute?
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