Question

I am reviewing 4 a final. Can u please help me solve:

Answer 1

Given

`u=15i-8j`

Find

Magnitude and direction of -3u.

Step-by-step explanation

given

u = 15i-8j

we have to find magnitude and direction of -3u.

so we multiply both sides by -3

-3u = -3(15i-8j) = -45i+24j

magnitude =

`\begin{gathered} magnitude=√(45^2+24^2) \\ magnitude=√(2025+576) \\ magnitude=√(2601)=51 \end{gathered}`

`\begin{gathered} \sin\theta_1=(24)/(51) \\ \theta_1=\sin^(-1)((24)/(51))=28\degree \\ so, \\ \theta=180\degree-28\degree=152\degree \end{gathered}`

Final Answer

Therefore , the correct option is 51; 152 degree that is option 4.