1. A store manager places ten paint cans into a rectangle five cans long and two
ID: 1874287 • Letter: 1
Question
1. A store manager places ten paint cans into a rectangle five cans long and two cans wide on the floor. He then tells an assistant to stack the remaining cans on the floor into a pyramidal display so that the second level is similar to the first. The third and fourth levels are each made up of eight cans arranged in a 4 x 2-can rectangle. The rest of the display should have every other remaining level decreasing by 2 cans. How much work does the assistant do in lifting the cans into position if each can weighs 46.0 N and is 0.20 m tall?Explanation / Answer
Workdone by assistant = workdone for 2nd + 3rd row + 4th row + 5th row + 6th row + 7th row
= increase in potential energy in every floor
= (5*2)*0.5*0.2 + (4*2)*46*2.5*0.2 + (4*2)*46*3.5*0.2 + (3*2)*46*4.5*0.2 + (2*2)*46*5.5*0.2 + (1*2)46**6.5*0.2
= 1013 J
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