Question

Please See The Attachment​

Answer 1

pls refer the attachment for better understanding

Refer the (2 nd picture)

tan x = QE /mg

As per the formula ,

T = 2π √ l /g (effective)

g effective = g² - (QE /m) ²

T = 2π √ l /g² - ( QE /m )²

the answer is d