$ABC$ is an equilateral triangle. Length of each side is $a$ and centroid is point $O$. then $\overrightarrow{O A}+\overrightarrow{O B}+\overrightarrow{O C}=.......$

A passenger arriving in a new town wishes to go from the station to a hotel located $10 \;km$ away on a straight road from the station. A dishonest cabman takes him along a circuitous path $23\; km$ long and reaches the hotel in $28 \;min$. What is

$(a)$ the average speed of the taxi,

$(b)$ the magnitude of average velocity ? Are the two equal ?

The vector that must be added to the vector $\hat i - 3\hat j + 2\hat k$ and $3\hat i + 6\hat j - 7\hat k$ so that the resultant vector is a unit vector along the $y-$axis is

A particle is moving along a circular path with a constant speed of $10\,ms^{-1}.$ What is the magnitude of the change in velocity of the particle, when it moves through an angle of $60^{o}$ around the centre of the circle .......... $m/s$

How many minimum number of coplanar vectors having different magnitudes can be added to give zero resultant

If vectors $P, Q$ and $R$ have magnitude $5, 12$ and $13 $ units and $\overrightarrow P + \overrightarrow Q = \overrightarrow R ,$ the angle between $Q$ and $R$ is