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How to carry groceries



Every time I get groceries with my mom I try to bring all of them in the house at once. She typically says, "You should take more trips!" But physics is on my side. It requires more work to bring in several loads of groceries opposed to just one big load. If work is a force x a distance than one big trip will require the least amount of work. To make one big load requires me to move the huge load of groceries, and myself once from the car into my house and into the kitchen. Simply taking two trips would require me to move myself from the car twice and back out to the car once. Splitting the groceries into two loads requires the exact same amount of work to move the groceries once because the force is halved but the distance is doubled. The issue of splitting the groceries into two or more loads is the work required to move myself is added. If assumed the distance is 20 meters from my house to the car and the groceries weigh about 100 kilograms then the force of the groceries is 1000N. The work required to move the groceries 20 meters is about 20,000 J. I weigh about 80 kilograms then the force of gravity is about 800N so it takes about 16000J to move myself. One trip of groceries would be 20,000 J + 16,000 J = 36,000J. Two trips would be 10,000 J(half the groceries) + 16,000 J + 16,000 J + 10,000 J +16,000J = 68,000 J. This is because I must move myself with the groceries 20 meters, then myself back to the car, then myself back inside with groceries again. By doing all of the work in one load I save 32,000 J of energy. Regardless of the load of groceries one big trip would save 32,000 J of work. It may be too difficult to carry all of the groceries at once but a load weighing perhaps weighing 20 kilograms is definitely manageable and effective in conserving energy if all done at once.


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