The position vector of a particle is determined by the expression $\vec r = 3{t^2}\hat i + 4{t^2}\hat j + 7\hat k$ The distance traversed in first $10 \,sec$ is........ $m$

In the picture shown, a ball standing from rest rolls down a ramp $AB$, goes along at the horizontal bottom $BC$, and then backs up a smaller ramp $CD$, thereafter rolls on horizontal plane $DE$. Ignore friction and air resistance.Which of the following figure shows variation in speed with time ?

Particles $A$ and $B$ are moving with constant velocities along $x$ and $y$ axis respectively, the graph of separation between them with time is

The position vector of a particle $\vec R$ as a function of time is given by $\overrightarrow {\;R} = 4\sin \left( {2\pi t} \right)\hat i + 4\cos \left( {2\pi t} \right)\hat j$ where $R$ is in meters, $t$ is in seconds and  $\hat i$ and $\hat j$  denote unit vectors along $x-$ and $y-$directions, respectively. Which one of the following statements is wrong for the motion of particle? 

A car travels $6 \,km$ towards north at an angle of $45^o $ to the east and then travels distance of $4 \,km$ towards north at an angle of $135^o $ to the east. How far is the point from the starting point. What angle does the straight line joining its initial and final position makes with the east

$Assertion$ : A tennis ball bounces higher on hills than in plains.
$Reason$ : Acceleration due to gravity on the hill is greater than that on the surface of earth