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16 August, 08:38

Jack and Jill are maneuvering a 3100 kg boat near a dock. Initially the boat's position is lesserthan 2, 0, 3 greaterthan m and its speed is 1.9 m/s. As the boat moves to position lesserthan 8, 0, 0 greaterthan m, Jack exerts a force of lesserthan - 420, 0, 210 greaterthan N, and Jill exerts a force of lesserthan 180, 0, 360 greaterthan N. a. How much work does Jack do? W_Jack = b. How much work does Jill do? W_Jill =

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  1. 16 August, 08:40
    0
    The mass of the boat is 3100kg.

    Initial position of boat is r1 = (2,0,3) m

    And initial velocity of boat is 1.9m/s

    New position r2 = (8,0,0) m

    Jill Force = (180,0,360) N

    Jack force = (-420,0,210) N

    a. Jack work

    Work is given as the dot product of force and displacement

    W=F•d

    The displacement is ∆r

    ∆r=r2-r1

    ∆r = (8,0,0) - (2,0,3)

    ∆r = (6,0,-3)

    The force exerted by Jack is Fj = (-420,0,210)

    Then,

    W=F•∆r

    W = (-420 i + 0 j + 210 k) • (6 i + 0j - 3 k)

    Then, i. i=j. j=k. k=1

    Also, i. j=j. i=k. i=i. k=j. k=k. j=0

    Using this principle

    Then,

    W = (-420 * 6) + (0*0) + (210*-3)

    W=-2520-630

    W=3150J.

    The workdone by Jack is 3150J

    2. Work done by jill

    Using the same principle and they have the same displacement

    ∆r = (6,0,-3)

    Therefore

    W=F•∆r

    W = (180 i + 0 j + 360 k) • (6 i + 0j - 3 k)

    Then, i. i=j. j=k. k=1

    Also, i. j=j. i=k. i=i. k=j. k=k. j=0

    Using this principle

    Then,

    W = (180 * 6) + (0*0) + (360*-3)

    W=1080-1080

    W=0J.

    The workdone by Jill is 0J, she did no work

    This show that Jill apply her force perpendicular to the displacement.

    Because W=0 if and only if the displacement is zero or it is perpendicular to the applied force

    3. I think we can still calculate the final velocity of the boat since we are given the mass

    Using conservation of energy principle

    ∆K. E=W

    K. E=1/2mv²

    Total work is 0+3150=3150J

    Then,

    0.5M (Vf²-Vi²) = W

    (Vf²-Vi²) = W/0.5M

    Given than M=3100kg and Vi=1.9m/s

    Vf²-Vi²=3150 / (0.5*3100)

    Vf²-1.9²=2.03

    Vf²=2.03+1.9²

    Vf²=5.6423

    Vf=√5.6423

    Vf=2.38m/s.
  2. 16 August, 08:56
    0
    A) WJack = - 3150 J

    B) WJill = 0 J

    Explanation:

    M = 3100kg and initial speed (u) = 1.9m/s

    Now, we know that work done = Force x displacement.

    So in this question,

    A) Work done by Jack (W) = F x Δr

    From the question, force applied by Jack equals (-420, 0, 210) N

    Also, since the boat moves from initial position of (2, 0, 3) m to final position of (8, 0, 0) m, thus the displacement (Δr) = (8, 0, 0) m - (2, 0, 3) m = (6,0, - 3) m

    Thus work done by Jack (W) =

    (-420, 0, 210) N x (6,0, - 3) m=

    ( - 420 x 6) + (0) + (210 x (-3)) =

    - 3150J

    B) Force applied by Jill = (180, 0, 360) N

    Using the same principle, work done by Jill = (180, 0, 360) N x (6,0, - 3) m =

    (180 x 6) + (0) + (360 x (-3)) = 0J
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