In a lab, two identical lab carts (m = 1.0 kg) travel toward each other, each with a speed of 2 m/s. the cars collide, and one cart moves to the right with a speed of 3 m/s and the other moves left with a speed of 2 m/s. what best explains the results of the experiment?

a. this experiment did not occur in a closed system.
b. this proves the conservation of momentum since pi = pf .
c. an additional mass was added to one cart, which explains the increase in speed.
d. the increase in speed was due to the kinetic energy from one cart transferring to the other.