Question

A uniform chain of length 3 metres and mass 3 kg overhangs a smooth table with 2 metres laying on the table. If k is the kinetic energy of the chain in joule as it completely slips off the table, then the value of k is ______.

(Take g = 10 m/s²)

Options

• 40J

• 30J

• 10J

• 20J

Answer 1

A uniform chain of length 3 metres and mass 3 kg overhangs a smooth table with 2 metres laying on the table. If k is the kinetic energy of the chain in joule as it completely slips off the table, then the value of k is 40J. 

Explanation:

When the chain collapses, the centre of mass shifts from `x_1 = 1/2` m to `x_2 = 3/2` m.

Based on mechanical energy conservation,

`Deltak = U_f - U_i`

= `(3 xx g xx 3/2) - (1 xx g xx 1/2)`

= 45 - 5 = 40J