The crane shown in the drawing is lifting a 172-kg crate upward with an accelera

Question

The crane shown in the drawing is lifting a 172-kg crate upward with an acceleration of 1.0 m/s2. The cable from the crate passes over a solid cylindrical pulley at the top of the boom. The pulley has a mass of 130 kg. The cable is then wound onto a hollow cylindrical drum that is mounted on the deck of the crane. The mass of the drum is 150 kg, and its radius is 0.76 m. The engine applies a counterclockwise torque to the drum in order to wind up the cable. What is the magnitude of this torque? Ignore the mass of the cable.

Explanation / Answer

Solved a similar question already.. i put the the question and the answer.. hope it helps.. kindly rate me :) the crane shown is the lifting a 180 kg crate up-ward with an acceleration of 1.2 m/s^2. the cable from the crate passes over a solid cylindrical pulley at the top of the boom. the pulley has a mass of 130 kg. the cable is then wound onto a hollow cylindrical drum that is mounted on the deck of the crane. the mass of the drum is 150 kg, and its radius is 0.76 m. the engine applies a counterclockwise torque to the drum in order to wind up the cable. (ignore the mass of the cable) ANSWER : Are you given the moment of inertia of the pulley and cylindrical drum, or only their masses? If the latter is true, ignore them. Torque = Moment Arm × Force Our moment arm = 0.76 meters. Our force = mass × acceleration. Our mass = 180 kg. Our acceleration = 1.2 m/s^2 + acceleration due to gravity = 1.2 m/s^2 + 9.8 m/s^2. So Torque = 0.76m × 180kg × (1.2 + 9.8)m/s^2 = 1.5 kN m if you round to 2 significant figures and use the kilonewtons times meters unit for torque. @Drostie: Why did you take into account the weight of the pulley? The pulley is being held by the boom, not the cable.

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