A particle is projected at an angle `alpha` with the horizontal from the foot of an inclined plane making an angle `beta` with horizontal . Which of the following expressions holds good if the particle strikes the inclined plane normally?

Options

A. `cot beta=-tan (alpha-beta)`
B. `cot beta=2 tan (alpha-beta)`
C. `cot alpha=tan (alpha-beta)`
D. `cot alpha=2tan (alpha-beta)`

Answer

b

Explanation

If the particle strikes normally then `v_(X)=0`
`v_(x)=u_(x)-g cos betaT`
`T=(2 u sin (alpha-beta))/(g cos beta)`