Two forces of magnitude $3\;N$ and $4\;N$ respectively are acting on a body. Calculate the resultant force if the angle between them is $0^{\circ}$. (in $;N$)

Explain the subtraction of vectors.

$A$ body moves due East with a velocity of $20 \, km/h$ and then due North with a velocity of $15 \, km/h$. The resultant velocity is .......... $km/h$.

When $n$ vectors of different magnitudes are added,we get a null vector. Then the value of $n$ cannot be

The resultant force of $5 \, N$ and $10 \, N$ cannot be ........ $N$.

With respect to a rectangular cartesian coordinate system,three vectors are expressed as $\vec a = 4\hat i - \hat j$,$\vec b = -3\hat i + 2\hat j$,and $\vec c = -\hat k$,where $\hat i, \hat j, \hat k$ are unit vectors along the $X, Y,$ and $Z$-axis respectively. The unit vector $\hat r$ along the direction of the sum of these vectors is: