Draw free body diagram including vectors
a) you are riding a bicycle down a hill while applying the brakes and skidding to a stop. assume that air resistance is negligible, but friction is not.

b) you jump off a bridge with a bungee cord attached to your ankle, and the cord stretches. assume air resistance is negligible.

c) a rocket is accelerating straight up through the earth's atmosphere. assume that air resistance is not negligible.

d) a meteoroid moves downward through the earth's atmosphere. its speed is decreasing. assume that air resistance is not negligible.