Opposite to the velocity vector

Perpendicular to the velocity vector

I don't know

$5-$ If you would have circularized the orbit when reaching Mars $($before entering the SOI$)$ and only after that entered the

sphere of influence, on what kind of trajectory would the spacecraft be$?($Even if this is an approximation, consider the SOI

is located at infinity to answer this question.$)$

Elliptical

Circular

Parabolic

Hyperbolic

You left the Earth using a space elevator, travelled to Mars, and you just performed the circularization at $400km$

altitude.

$6-$ What is the final mass of the spacecraft $($in $kg)?$