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Answer:
the work done in pulling the bucket to the top of the well is 2125 ft-lb
Step-by-step explanation:
Given that;
Weight of the bucket is 3 lb
weight of water which can be filled in the bucket is 42 lb
Total weight of bucket and water = 3 + 42 = 45 lb
distance, the bucket filled with water is to be pulled 50 ft
now, let at any time t be the bucket at distance x ft from the bottom of the well
then, t = x/2 × S
where S is the rate at which water is leaking from the bucket
so at this time t, the amount pf water which leaked from the bucket is;
⇒ x ft / 2.5 ft/s × 0.25 lb/s
= 0.25 lb.s⁻¹ / 2.5 ft.s⁻¹ × x ft
= 0.1 lb/ft × x ft
= 0.1x lb
now, as x represent the distance that the bucket has been raised, we the force F applied to the bucket x to be;
F = ( 45 - 0.1x ) lb
so, the required worked by Riemann sum as;
[tex]\lim_{n \to \infty}[/tex]ⁿ∑_[tex]_{i=1}[/tex] ( 45 - 0.1x[tex]_i[/tex]* ) Δx
so, the work done, pulling the bucket up will be;
[tex]\lim_{n \to \infty}[/tex]ⁿ∑_[tex]_{i=1}[/tex] ( 45 - 0.1x[tex]_i[/tex]* ) Δx = [tex]\int\limits^{50}_0 {(45-0.1x)} \, dx[/tex]
= [ 45x - 0.1[tex]\frac{x^2}2}[/tex] ]⁵⁰₀
= 45 × 50 - 0.1/2 × (50)²
= 2250 - 125
= 2125 ft-lb
Therefore, the work done in pulling the bucket to the top of the well is 2125 ft-lb