hi

let us take the initial velocity of car be 'u'

thus p=mu

final velocity = v = 0 nd since car stops after a certain distance hence it is retarding

we know that v^2=u^2+2as

thus 0=u^2-2as

therefore s=u^2/2a - (1)

now when momentum is 2p, obviously the velocity becomes 2u so substituting (2u) in place of u then s'=4u^2/2a=4s.

hey it was rather a simple question