A particle is projected from a trolley car with a velocity $\overrightarrow{\mathrm{v}}$. If the trolley car moves with an acceleration $\overrightarrow{\mathrm{a}}$ towards right, which of the following remain unchanged relative to both ground and trolley car?

Vertical component of projectile relative to trolley,

${\mathrm{v}}_{\mathrm{yT}} = \mathrm{v} \sin \mathrm{\theta }$

And vertical component of projectile relative to ground

${\mathrm{v}}_{\mathrm{yG}} = \mathrm{v} \sin \mathrm{\theta }$

Vertical component is unchanged relative to trolley and ground.

Now time of flight = $\frac{2\mathrm{u} \mathrm{sin\theta }}{\mathrm{g}}$

Time of flight remains unchanged relative to trolley & ground.