A 3.50kN piano is lifted by 3 workers at a constant speed to an apartment 25.0m above the street, using a pulley system fastened to the roof of the building. Each worker can deliver 165 W of power, and the pulley system is 75% efficient. Neglecting the mass of the pulley and ropes, find the time for the workers to lift the piano from the street to the apartment window.

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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1.195000

explanation:

total mass=0.0117+0.0137+0.0881+0.0111

total mass= 0.01172kg

total velocity = 0.283-0.743+0.871-0.799+0.155+0.637+0.301=0.102

momentum=mv=0.1172*0.102=1.195000//