Two blocks are hung by a string draped over a pulley, a 1.3-kg block on the left and a 3.0-kg block on the right. The two blocks start out at rest and at the same height. Required:
a. What is the change in the gravitational potential energy of the system of blocks and Earth when the 2.9-kg block has dropped 0.61 m?
b. What is the change in the kinetic energy of the system between release and this instant?
c. What is the velocity of the 1.3-kg block at this instant?

answer: decibel

explanation:

as we know our atmosphere or air have different levels. every level has other gasses, and every gas has another permeability. when the light comes from lower permeability to higher permeability, it changes its direction. so that means that when the light comes from the moon to the earth, it changes it's direction many more times. it basically means that the shape of the light part of the moon is changed on the earth.

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