Given that $P + Q + R =0$. Which of the following statement is true?

Three concurrent forces of the same magnitude are in equilibrium. What is the angle between the forces  Also name the triangle formed by the forces as sides

A particle is situated at the origin of a coordinate system. The following forces begin to act on the particle simultaneously (Assuming particle is initially at rest)

${\vec F_1} = 5\hat i - 5\hat j + 5\hat k$            ${\vec F_2} = 2\hat i + 8\hat j + 6\hat k$

${\vec F_3} =  - 6\hat i + 4\hat j - 7\hat k$         ${\vec F_4} =  - \hat i - 3\hat j - 2\hat k$

Then the particle will move

Two forces of magnitude $P$ & $Q$ acting at a point have resultant $R$. The resolved  part of $R$ in the direction of $P$ is of magnitude $Q$. Angle between the forces is :

$\overrightarrow A \, = \,2\widehat i\, + \,3\widehat j + 4\widehat k$ , $\overrightarrow B \, = \widehat {\,i} - \widehat j + \widehat k$, then find their substraction by algebric method.

The coordinates of a moving particle at any time $t$ are given by $x = a\, t^2$ and $y = b\, t^2$. The speed of the particle is