Question

A system to 10 balls each of mass 2 kg are connected via massless and unstretchable string. The system is allowed to slip over the edge of a smooth table as shown in figure. Tension on the string between the 7th and 8th ball is ______ N when 6th ball just leaves the table.

Fig. Tension on String

Answer 1

The correct answer is 36N
At given instant
$a_{sys} = \frac{6m × g }{ 10m} = \frac{6g}{100}$
$∴ T_{78} = ( 3m ) × a_{sys}$
$= ( 3m ) × ( \frac{6g}{100} )$
$= \frac{3 × 2 × 6 × 10 }{10}$
$= 36N$