If a unit vector is represented by $0.5\hat i + 0.8\hat j + c\hat k$,then the value of $c$ is

What is the minimum number of coplanar vectors of different magnitudes whose sum can be zero?

If water at $100^\circ C$ cools in $10$ minutes to $80^\circ C$ and to $65^\circ C$ in the next $10$ minutes, then the room temperature will be ...

If $A = 3\hat i + 4\hat j$ and $B = 7\hat i + 24\hat j,$ the vector having the same magnitude as $B$ and parallel to $A$ is

The angle made by the vector $(\hat{i} + \hat{j})$ with the $x$-axis and $y$-axis is:

$A$ vector $\overrightarrow{a}$ is turned without a change in its length through a small angle $d\theta$. The values of $|\Delta \overrightarrow{a}|$ and $\Delta a$ are respectively: