Assuming that the air temperature is constant, what happens to a hot air balloon if it goes too far up in the atmosphere , where the outside air pressure is much less than the inside are pressure of the balloon? . a. it bursts. b. it loses air . c. it burns up. d. gravity begins to pull it back down to earth

Asled is being held at rest on a slope that makes an angle θ with the horizontal. after the sled is released, it slidesa distance d1 down the slope and then covers the distance d2 alongthe horizontal terrain before stopping. find the coefficient ofkinetic friction μk between the sled and the ground, assumingthat it is constant throughout the trip. find the coefficient of kinetic frictionμk. express your answer in terms of someor all of the variables d1, d2, and θ.