Mark the correct statement :-

- A
$| \vec a + \vec b | \geq | \vec a | + | \vec b |$

- B
$| \vec a + \vec b | \leq | \vec a | + | \vec b |$

- C
$| \vec a - \vec b | \geq | \vec a | + | \vec b |$

- D
All of the above

Two forces of magnitude $8 \,N$ and $15 \,N$ respectively act at a point. If the resultant force is $17 \,N$, the angle between the forces has to be .......

A plane is revolving around the earth with a speed of $100\, km/hr $ at a constant height from the surface of earth. The change in the velocity as it travels half circle is.........$km/hr$

Find unit vector perpendicular to $\vec A$ and $\vec B$ where $\vec A = \hat i - 2\hat j + \hat k$ and $\vec B = \hat i + 2\hat j$

Give equation to find the value of resultant vector and the direction of two vectors.

A cyclist starts from the centre $O$ of a circular park of radius $1\; km$, reaches the edge $P$ of the park, then cycles along the circumference, and returns to the centre along $QO$ as shown in Figure. If the round trip takes $10 \;min$, what is the

$(a)$ net displacement,

$(b)$ average velocity, and

$(c)$ average speed of the cyclist ?