A ball is moving with speed `20 ms^(-2)` collides with a smooth surface as shown in figure. The magnitude of change in velocity of the ball will be

Options

A. `10sqrt(3)ms^(-1)`
B. `20sqrt(3)ms^(-1)`
C. `(40)/(sqrt(3))ms^(-1)`
D. `40ms^(-1)`

Answer

B

Explanation

(b) `v_(i)=-v sin 60 hati-v cos 60 hatj`
`v_(f)=-v sin 60 hati+v cos 60 hatj`
`therefore v=v_(f)-v_(i)=+2xx20xx(sqrt(3))/(2) = 20sqrt(3) ms^(-1)`