The minimum acceleration with which a fireman can slide down a rope of breaking strength two - third of his weight is

Options

A. zero
B. ` ( g ) / ( 3 ) `
C. `3g `
D. ` g `

Answer

B

Explanation

If fireman slides down with some acceleration then its apparent weight decreases. For critical condition rope can bear only ` ( 2 )/( 3 ) ` of the fireman's weight. Let ` alpha ` is the minimum acceleration then,
Tension in the rope ` = m ( g - a ) ` = Breaking strenght
` rArr m ( g-a ) = ( 2 )/ (3 ) mg `
` rArr a = g - ( 2g ) /( 3 ) = ( g )/(3 ) `