When earth catches up to a slower-moving outer planet and passes it in its orbit the planet

a. exhibits retrograde motion.
b. slows down because it feels earth's gravitational pull.
c. decreases in brightness as it passes through earth's shadow.
d. moves into a more elliptical orbit.

a. exhibits retrograde motion.

Explanation:

When earth catches up to a slower moving outer planets like for example Saturn and jupitar they seems to show the retrograde motion which is actually an illusion but there exits the real retrograde motion too in some cases. In retrograde motion planets appears to move in the backward direction like from east to west rather then from west to east in the sky.

the chart show the masses and velocities of two colliding objects that stick together after a collision.

according to the law of conservation of momentum, the momentum of the object after the collision is  

answer

1,500

kg • m/s.

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