The correct answer is Destructive Interference.Consider the image attached below. Two waves are travelling towards each other. Blue wave always has a positive peak and the red wave always has a negative peak.
Now imagine these waves are moving through a rope. If blue waves will try to move the rope in positive direction, the red wave will pull it down, and thus the two waves will cancel the effect of each other. Thus resulting in a destructive interference.
Answer:

Explanation:
Given data:
L =2.00 *10^4 m
d = 18*10^4 m
M = 18 *10^6 kg
m_1 = 8*10^6 kg
Gravitational energy is given as

mass per unit length is given as

calculating potential energy







Answer:
c. is negative
Explanation:
When the magnitude of force is multiplied with the force vector's projection along the direction of the vector of displacement which is negative as it is a resistive force we get the work done.
As the wind is acting in opposite direction of the force which is being applied by the plane the work done will be negative. Also, the net work will be the sum of many smaller negative quantities.
Hence, the answer here is negative.