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Question
A 144lb bag of sand is lifted at a constant rate. At 18ft half the sand is gone. How much work has been done?
Hi Tyson,
I'm assuming that sand is leaving the bag at a constant rate.
So the amount of sand at a given distance d is 144-4d.
So since work is integral (Force times distance we have)
work = int from 0 to 36 of (144-4d)
= (144d - 2d^2) from 0 to 36
So it is
144*36 - 72*36 = 72*36 = 2592 ft lbs.
I hope this helps,
Robi
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Answers by Expert:
Robi Bhattacharjee
Expertise
I can answer a variety of questions on mathematics. Questions on trigonometry, calculus(preferably single variable), algebra, geometry, and number theory will be answered. I cannot answer questions on abstract branches of mathematics such as group theory. I also cannot answer questions on statistics. In number theory, I can answer questions on congruences, prime numbers, units, functions, and the riemann-zeta function.
Experience
I have studied advanced math my entire life. I started calculus in sixth grade. I have attended numerous math competitions and I am attending math organizations such as the San-Diego math circle. Also, this year I have been invited to the USAMO which is a prestigious math competition (Every year the USAMO invites 500 students from across the USA to participate in this competition. The top 6 go to represent the USA in the International Math Olympiad).
Organizations
I am in the San Diego Math Circle
Education/Credentials
I am entering high school and have received a perfect score and the STAR test 5 times in a row. I also have gotten recognitions in the AMC 10, AIME, Math Counts, and ARML. Additionally, I have won the San Diego Math Olimpiad twice in a row.
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