A body of mass 5 kg is acted upon by a constant force`vecF=(-3overset(wedge)(i)+6overset(wedge)(j))N`Its initial velocity at t = 0 is`vecu = (6overset(wedge)-2overset(wedge)ms^(-1)` what is its velocity after 5s ? What is its magnitude ? 

Options

A. `(3overset(wedge)(i)+6overset(wedge)(j)),5ms^(-1)`
B. `(2overset(wedge)(i)-2overset(wedge)(j)),2sqrt(2)ms^(-1)`
C. `(3overset(wedge)(i)-4overset(wedge)(j)),5ms^(-1)`
D. `(2overset(wedge)(i)-3overset(wedge)(j)),sqrt13ms^(-1)`

Answer

a

Explanation

Here `vecF=(-3hati+6hatj)N`
`m=5kg`
`:.veca=(-3hati+6hatj)/(5)`
Now `vecupsilon=vecu+vecat`
`=(6hati-2hatj)+(-3hati+6hatj)/(5)xx5`
`=(6hati-2hatj)-3hati+6hatj`
`vecupsilon=(3hati+4hatj)`
`|upsilon|=sqrt(9+16)=5ms^(-1)`
Hence (a) is the right choice.