*Simple Pendulum Viva Questions and Answers*

**(i) Who invented simple pendulum?**

Ans: Galileo

**(ii) Is `g' a vector quantity?**

Ans: yes

**(iii) What is the effective length of a simple pendulum?**

Ans: It is the total length from the point of suspension to
the centre of gravity of the bob

**(iv) Why do we use heavy bob which is small in size?**
Ans: A heavy bob has enough restoring force to overcome the
air resistances. A small bob has less resistance due to air. So heavy bob,
small in sizes is used as bob

**(v) What is a seconds pendulum?**
Ans: It is a simple pendulum whose time period is 2 seconds.
It takes one second to move from one extreme position to the other end.

**(vi) If the given bob is replaced by a wooden bob of the same size will the time period change?**
Ans: It remains the same

**(vii) What will happen to the time period if a simple pendulum is setup on the surface of the moon?**
Ans: The time period will increase as the value of 'g' on
the surface of the moon in less than that on the surface of the earth.

**(viii) While oscillating, the amplitude of the pendulum must be small-why?**
Ans: For small amplitude sin θ = θ in radians. Then the simple
pendulum has simple harmonic oscillations.

**(ix) What is the relation between 'g' and 'G'? Gin**
Ans: g = Gm/R

^{2}

**(x) What is the value of 'g' at the centre of the earth?**
Ans: zero.

**(xi) If you set up a simple pendulum in an artificial satellite orbiting the earth what will be the period of the pendulum?**
Ans: Inside the satellite g = 0. Hence period is infinite.

**(xii) Apparatus of the Simple Pendulum**
Ans: A simple pendulum, stop clock, metre scale, vernier
calipers, stands etc. The simple pendulum consists of a metallic bob suspended
by a light inextensible string passing through the split halves of a cork.

**(xiii) Theory of Simple Pendulum**
Ans:The period of a simple pendulum of length

*l*at a place where the acceleration due to gravity is g, which is given by,
T = 2π √(

*l*/g);
Therefore, g = 4 π

^{2}(*l*/T^{2})

**(xiv) Aim of the Simple Pendulum Experiment**
Ans: (a) To determine the acceleration due to gravity at the
place.

(b) To draw

*l*– T^{2}graph and hence to find the length and period of the Pendulum.

**(xv) Procedure of the Simple Pendulum Experiment**

__(a) To find the acceleration due to gravity at the place__
The period
of oscillation, T = (t/30), is calculated. The experiment is repeated with different
lengths l (60, 70, 80 ………….. cm) of the pendulum. In each case l/T

^{2}is calculated. In all cases it is found that (l/T^{2}) is a constant. The average value of (l/T^{2}) is determined and the acceleration due to gravity (g) is calculated. g = 4π^{2}(l/T^{2})

__(b) To draw T__^{2}— I graph
The
experiment is performed as explained above. A graph is drawn with l along the
X-axis and T

^{2}along the Y-axis. This graph is a straight line.
(i) To find
the length of the seconds pendulum

A seconds
pendulum is one for which the period of oscillation is 2 seconds. From the
graph the length 1 corresponding to T

^{2}= 4 is determined. This gives the length of the seconds pendulum.
(ii) To
find the length of the pendulum whose period is 1.5 seconds, the length l corresponding
to T

^{2}= 1.5^{2}= 2.25 is determined from the graph.
(iii) From
the graph, 1/T

^{2}= AB/BC. Therefore, g = 4π^{2}(AB/BC)
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