Question

Hi everyone
how to find force in Q.(a)(ii)
https://www.physicsforums.com/attachments/whatsapp-image-2016-12-11-at-9-58-01-pm-jpeg.110259/

thank you very much

Answer 1

the Force has magnitude 14N and acts in the direction of your unit vector \(\hat e\) from Pt (i) so it's \(\vec F = F \hat e\)

Answer 2

Do you want hint or the complete answer?

Answer 3

But I think the answer will be incorrect since there is nothing told about the time taken in the displacement.

Answer 4

like this?
but how can get the answer as a vector?

Answer 5

That is a vector, which is why the F is now wearing a little arrow on it's head :) but maybe add brackets to get

\(\vec F = \dfrac{14}{\sqrt{3}}(\hat i + \hat j + \hat k ) \)

if it looks odd to you, remember its magnitude is

\(|\vec F| = \sqrt{\left( \dfrac{14}{\sqrt{3}} \right)^2 + \left( \dfrac{14}{\sqrt{3}} \right)^2 + \left( \dfrac{14}{\sqrt{3}} \right)^2} = 14N\) which is where you started out.

You just added information about it's direction into the picture


maybe you are worried about aesthetics?!


you can drop the i,j,k for a slightly more expressive

\(\vec F = \dfrac{14}{\sqrt{3}}<1,1,1> \)


or

\(\vec F = \dfrac{14}{\sqrt{3}} \left( \begin{matrix}
1 \\
1 \\
1
\end{matrix} \right)
\)

any notation you like as long as it's consistent