Can the direction of the velocity of the body be changed when it's acceleration is constant ?

No

Explanation:

Acceleration means the change in velocity. Since velocity is a vector of speed and direction, if your direction is changing you can be accelerating without changing your speed. So if the direction of the velocity changes, so will the acceleration. Hope this helps!

force is mass*acceleration.

we have a very small mass: 11.4*0.001 kg

if we want 0.035n of force, we need an acceleration:

0.035 = 11.4*0.001*a

a = 0.035/(11.4*0.001) m/s^2

their crystal patterns have been disrupted by stress