The halide used widely in photography is

Silver halide or silver salt is mostly used in photographic films

Explanation:

Silver halide crystals in gelatin are coated onto a film base, glass or paper substrate. And when a sliver halide crystal is exposed to light (photons strike) it turned into a small speck of metallic crystal and these comprise the invisible or latent image which is developed afterwards.

what was the acceleration of the 2 kg cart?

⇒ 16.0 cm/s2

what was the acceleration of the 4 kg cart?

⇒ 8.1 cm/s2

what was the acceleration of the 6 kg cart?

⇒ 5.3 cm/s2

increase masses, decrease separation