Crane lifting crate

  • #1

Homework Statement



The crane shown in the drawing is lifting a 186-kg crate upward with an acceleration of 2.0 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.

Homework Equations



torque= I*angular acceleration
I= mr^2
angular accel= accel/r



The Attempt at a Solution




I tried everything that i know

angular accel= 2/.76 =2.6316 rad/s^2
I=150*.76^2= 86.64
torque= 86.64*2.6316= 228 N*m

But this answer is wrong. I tried negitive and thats wrong. What am I doing wrong! lol.
 

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