Question

sofia and marcus tie a ribbon to a hook and place two identical portable air - conditioning units near it. when they turn on both units to different settings, the ribbon starts to flutter toward the right. sofia claims she can balance the forces on the ribbon without turning either unit off. which of the following would most likely produce the change in motion necessary to support sofias claim? a change the setting of a/c unit 2 so it is blowing the same amount of air as a/c unit 1. b point a/c unit 2 upward so it is blowing toward the ceiling. c move a/c unit 2 so that both units are blowing on the left side of the ribbon. d move a/c unit 2 so that it is farther from the ribbon than a/c unit 1.

Explanation:

To balance the forces on the ribbon without turning off either unit, the air - flow forces from both units need to be equal and opposite. Changing the setting of A/C Unit 2 so it blows the same amount of air as A/C Unit 1 would create equal and opposite air - flow forces on the ribbon, potentially balancing it. Pointing A/C Unit 2 upward changes the direction of the force but not in a way to balance the horizontal forces on the ribbon. Moving A/C Unit 2 to blow on the same side of the ribbon or making it farther from the ribbon will not balance the forces in the horizontal direction.

Answer:

A. Change the setting of A/C Unit 2 so it is blowing the same amount of air as A/C Unit 1.