Question

The length of the string of a simple pendulum is measured with a metre scale to be 90.0 cm, The radius of the bob plus the length of the hook is calculated to be 2.13 cm using measurements with a slide callipers.
What is the effective length of the pendulum ? (The effective length is defined as the distance between the point of suspension and the centre of the bob.)

Answer 1

As shown in the figure,

Actual Effective length = (90.0+2.13) cm But, in the measurement 90.0 cm, the no. of significant digits is only 2.

So, the addition must be done by considering only 5 significant digits of each point.

So, effective length = 90.0+2.1 = 92.1 cm.