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29 March, 06:12

Block B starts from rest, block A moves with a constant acceleration, and slider block C moves to the right with a constant acceleration of 75 mm/s2. Knowing that at t = 2 s the velocities of B and C are 480 mm/s downward and 280 mm/s to the right, respectively, use kinematics to determine:

a. The acceleration of A and B

b. The initial velocities of A and C

c. The change in positions of slider C after 3 s.

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  1. 29 March, 06:39
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    a) aB = 240 mm/s² (↓)

    aA = - 345 mm/s²

    b) For the Block C

    v₀ = 130 mm/s

    For the Block A

    v₀ = - 43.33 mm/s

    c) Δx = 727.5 mm

    Explanation:

    a) For the Block B

    v = v₀ + a*t

    480 = 0 + a * (2)

    aB = 240 mm/s² (↓)

    Then we have

    3*LA + 4*LB + LC = L

    If we apply

    d (3*LA + 4*LB + LC) / dt = dL/dt

    3*vA + 4*vB + vC = 0

    d (3*vA + 4*vB + vC) / dt = d (0) / dt

    3*aA + 4*aB + aC = 0

    aA = - (4*aB + aC) / 3

    aA = - (4*240 mm/s² + 75 mm/s²) / 3

    aA = - 345 mm/s²

    b) For the Block C

    v = v₀ + a*t

    v₀ = v - a*t

    v₀ = 280 - (75) (2) = 130 mm/s

    For the Block A

    When t = 2 s

    vB = 480 mm/s

    vC = 280 mm/s

    we use the formula

    3*vA + 4*vB + vC = 0

    3*vA + 4 * (480) + 280 = 0

    vA = - 733.33 mm/s

    Now, we can apply

    v = v₀ + a*t

    - 733.33 mm/s = v₀ + ( - 345 mm/s2) (2 s)

    v₀ = - 43.33 mm/s

    c) We can use the equation

    Δx = v₀*t + (1/2) * a*t²

    Δx = 130 * (3) + (1/2) (75) (3) ²

    Δx = 727.5 mm
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