A point mass of 2 kg tied to a string of 1 m length is rotated in a vertical circle with uniform speed of 4m/s. The tension in the string is nearly 32 N when mass is at

Options

A. botton
B. mid- way
C. highest point
D. between bottom and mid way

Answer

A

Explanation

Tenesion in the string at any point is
` T - mg cos theta = ( mv ^ 2 )/( r ) `
` rArr T= ( mv ^ 2 ) /( r ) + mg cos theta `
` rArr 52 = ( 2xx 16 )/( 1 ) + 2xx 10 cos theta `
` = 22 + 20 cos theta `
` rArr 20 = 20 cos theta `
` rArr cos theta = 1 `
` rArr theta = 0^@ `
` therefore ` Mass is at the bottom of circle.