In the question number 52, the speed with which the stone hits the ground is

Options

A. 15 m `s^(-1)`
B. 90 m `s^(-1)`
C. 99 m `s^(-1)`
D. 49 m `s^(-1)`

Answer

C

Explanation

Motion along horizontal direction, `downarrow +ve`
`u_(x) = 15 ms^(-1), a_(x) = 0`
`v_(x) = u_(x) + a_(x)t = 15 + 0 xx 10 = 15 ms^(-1)`
Motion along vertical direction,
`u_(y) = 0, a_(y) = g`
`v_(y) = u_(y) + a_(y)t = 0 + 9.8 xx 10 = 98 ms^(-1)`
`therefore` Speed of the stone when it hits the ground is
`v = sqrt(v_(x)^(2) + v_(y)^(2)) = sqrt((15)^(2) + (98)^(2)) ~~ 99 ms^(-1)`