The length of a seconds pendulums is 100 cm. To have a period half of this value the length is to reduced by

Options

A. 25cm
B. 75cm
C. 50cm
D. 100cm

Answer

B

Explanation

`T_(2)=(1)/(2)T_(1)`
`(T_(2))/(T_(1))=sqrt((l_(2))/(l_(1)))`
`(1)/(2)=sqrt((l_(2))/(l_(1)))`
`(1)/(4)=(l_(2))/(l_(1))`
`l_(2)=(1)/(4)=0.25m=25cm`
`l_(1)-l_(2)=100-25=75cm`