MCQ
In an experiment on simple pendulum to determine the acceleration due to gravity, a student measures the length of the thread as $63.2 \,cm$ and diameter of the pendulum bob as $2.256 \,cm$. The student should take the length of the pendulum to be ........... $cm$
  • A
    $64.328$
  • $64.3$
  • C
    $65.456$
  • D
    $65.5$

Answer

Correct option: B.
$64.3$
b
(b)

Length of pendulum = Length of thread + Radius of bob

$=63.2+\frac{2.256}{2}=63.2+1128$

$=64.328 \,cm$

But now the student must apply rule for taking significant digits in a measurement.

In addition or subtraction,

Number of digits after decimal in result

= Least number of digits after decimal in quantities added

So, length of pendulum $=64.3 \,cm$.

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