While analysing a head-on collision, a student obtains a negative value for the initial velocity of one of the bodies. What does the negative sign indicate?
(a) The negative sign indicates the body was slowing down (decelerating) before collision.
(b) The body was moving opposite to the chosen positive direction before collision.
(c) The calculation is invalid because speed cannot be negative.
(d) The negative sign shows that the body would rebound backward after the impact rather than before it.