A jet airplane travelling at the speed of $500 km h^{-1}$ ejects its products of combustion at the speed of $1500 km h^{-1}$ relative to the jet plane. What is the speed of the latter with respect to an observer on the ground?

$1. 1000 km h^{-1}$
$2. 500 km h^{-1}$
$3. 1500 km h^{-1}$
$4. 2000 km h^{-1}$

A police van moving on a highway with a speed of $30 km h^{-1}$ fires a bullet at a thief’s car speeding away in the same direction with a speed of $192 km h^{-1}$. If the muzzle speed of the bullet is $150 m s^{-1},$ with what speed does the bullet hit the thief’s car? 

$\left(1\right) 103 m s^{-1}$
$\left(2\right) 105 m s^{-1}$
$\left(3\right) 101 m s^{-1}$
$\left(4\right) 102 m s^{-1}$

On a long horizontally moving belt (as shown in the figure) a child runs to and fro with a speed $9 km h^{-1}$ (with respect to the belt) between his father and mother located 50 m apart on the moving belt. The belt moves with a speed of $4 km h^{-1}$. For an observer on a stationary platform outside, what is the speed of the child running in the direction of motion of the belt?

1. 5 kmh^-1
2. \(\sqrt{41}\) kmh^-1
3. 21 kmh^-1
4. 13 kmh^-1