Why does light splits into different colours while passing through a prism

Since different colours of light travel at different speeds, the refractive index is different for each colour. As a result, when light passes through the refracting surface of the prism,its components bend into different angles, causing the single beam of light to separate

one person pulls 90n one way and the other has 100n pulling the other way.

so the net force = 90 - 100 = -10n,

or the ans can be 10n if the picture shows -90n and 100n instead.