The end B of the rod AB which makes angle `theta` with the floor is being pulled with a constant velocity `v_(v)` as shown. The length of the rod is `l`.

Options

A. `3/5v_(0)`
B. `4/5v_(0)`
C. `5/3v_(0)`
D. `5/4v_(0)`

Answer

B

Explanation

Let `OA=x, OB=y`
`x^(2)+y^(2)=l^(2)` and `x=lcostheta`
Different `x^(2)+y^(2)=l^(2)` with respect to time.
`2x(dx)/(dt)+2y(dy)/(dt)=0`
`V_(B)=(dy)/(dt)=x/y (dx)/(dt)=-V_(A)cottheta=4/5v_(0)darr`