If the velocity is `vec(v) = 2 hat(i) + t^(2) hat(j) - 9 vec(k)`, then the magnitude of acceleration at t = 0 . 5 s is :

Options

A. `1 ms^(-2)`
B. `2 ms^(-2)`
C. zero
D. `-1 ms^(-2)`

Answer

A

Explanation

`vec(v) = 2 hat(i) + t^(2) hat(j) - 9 hat(k)`
`vec(a) = (dvec(v))/(dt) = 2 t " ":. t = 0 . 5 `
`vec(a) = 2 xx 0.5 = 1ms^(-2)`