Miko is blowing up balloons for her little sister's birthday party. One of the balloons slips out of her hand before she ties it off, and it shoots through the air until it is empty. Which statement explains what causes the balloon to accelerate ?
A. The air leaving through the balloon's mouth pushes on the air surrounding the balloon, so the balloon experiences a net force.
OB. All air surrounding the balloon pushes the balloon forward.
OC. The mass of the air leaving the balloon is greater than the mass of the balloon, so the balloon moves forward.
OD. When the balloon pushes on the leaving air, the leaving air pushes back on the balloon, so the balloon experiences a net force.

Arunner is jogging at a steady 3.6 km/hr. when the runner is 2.9 km from the finish line, a bird begins flying from the runner to the finish line at 14.4 km/hr (4 times as fast as the runner). when the bird reaches the finish line, it turns around and flies back to the runner. even though the bird is a dodo, we will assume that it occupies only one point in space, i.e., a zero-length bird. how far does the bird travel? (b) after this first encounter, the bird then turns around and flies from the runner back to the finish line, turns around again and flies back to the runner. the bird repeats the back and forth trips until the runner reaches the finish line. how far does the bird travel from the beginning? (i.e. include the distance traveled to the first encounter)