After a projectile is fired into the air, what is the acceleration in the x-direction? (assume no air resistance.)

Explanation:

When projectile is in air then the force on the projectile is only due to its weight

It is vertically downwards

so here since we don't have any air drag or friction due to air so there will be no force along its tangent or along x direction

so the acceleration along x direction will be zero

i think the answer would be b

massxgravity x heght=weightxheight= pe

4900=490xh

h=10