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The truck at B is used to hoist the cabinet up to the fourth floor of a building

ID: 1822900 • Letter: T

Question

The truck at B is used to hoist the cabinet up to the fourth floor of a building using the rope and pulley arrangement. The truck has a speed of vB = 2 ft/s, and is accelerating at aB = 0.6 ft/s2. Determine the acceleration of the cabinet when sA = 40 ft. Note that when sB = 0, sA = 0 (points A and B are coincident).

The truck at B is used to hoist the cabinet up to the fourth floor of a building using the rope and pulley arrangement. The truck has a speed of vB = 2 ft/s, and is accelerating at aB = 0.6 ft/s2. Determine the acceleration of the cabinet when sA = 40 ft. Note that when sB = 0, sA = 0 (points A and B are coincident).

Explanation / Answer

when the the truck is at a distance x, let the cabinet is moved a distance y upwards.

Let the point at pulley = P

PA + PB is always constant

PA + PB = 100

50-y + (x^2 + 2500) = 100

(y + 50)^2 = x^2 + 2500

y^2 + 100y + 2500 = x^2 + 2500

y^2 + 100y = x^2, when y = 40, x = 74.833

2ydy/dt + 100dy/dt = 2xdx/dt

2*40*dy/dt + 100dy/dt = 2*74.83*2

dy/dt = 1.66

2yd^y/dt^2 + 2(dy/dt)^2 + 100d^2y/dt^2 = 2xd^2x/dt^2 + 2(dx/dt)^2

2*40*a + 2*1.66^2 + 100a = 2*78.33*0.6 + 2*2^2

a = 0.536 ft/s^2