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Title: Conical Pendulum
Aim: See your laboratory manual
Apparatus: See your laboratory manual
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THEORY:
A conical pendulum is a
pendulum that is spun round in a circle instead of swung backwards and
forwards. In this experiment a mass is attached to a string and made to spin in
a circle of fixed radius, the time period of the motion is related to the
length of the string. By varying the length and measuring Time period the
acceleration of gravity can be found.
**GENERAL KNOWLEDGE**
A conical pendulum is
a weight (or bob) fixed on the end of a string (or rod) suspended from a pivot.
Its construction is similar to an ordinary pendulum; however, instead of
rocking back and forth, the bob of a conical pendulum moves at a constant speed
in a circle with the string (or rod) tracing out a cone. The conical pendulum
was first studied by the English scientist Robert Hooke around 1660 [1]
as a model for the orbital motion of planets. Later it was used as the
timekeeping element in a few mechanical clocks and other clockwork timing
devices.
THEORY 1:
Above is a free body diagram
for the mass. If the forces are resolved vertically and horizontally:
Vertically the forces are balanced so mg=Fcosθ
Where F is the tension
Horizontally there is centripetal acceleration so mω2r=Fsinθ
Where
m = mass
ω = Angular velocity
r = radius
ω = Angular velocity
r = radius
Dividing gives
mg/mω2r =Fcosθ/Fsinθ =1/ tanθ
But
tanθ = r/h
so,
ω2r/g=
r/h
from the definition
ω = 2π/T so 4π2/gT2 = 1/h
Where T = time period
Squaring gives
h2 = g2T4/16π4
From Pythagoras L2 = h2
+ r2 so h2=L2 – r2
Finally
L2=g2T4/16π4
+ r2
By changing L and measuring T keeping r constant use a
graphical method to find g.
For Procedures, See your Mechanical Laboratory Manual.
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Observations :-
1.
Applications:-
1.
PRECAUTIONS:
For
Precautions, See General Laboratory Precautions
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