What is the Kinetic Energy of a Pulley System with Bodies B1, B2, and B3?

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Homework Statement


http://s2.webstarts.com/exploring-my-thought/index.html

Find the kinetic energy of the system of bodies B1, B2 and B3 at an instant when the speed of B1 is 5ft/sec (the image is linked above)

radius of B2 = 2ft
mass of B1 = 32.2lb
mass of B2 = 32.2lb
mass of B3 = 96.6lb

answer is 25ft-lb

Homework Equations


translational kinetic energy: K = 1/2mv2
rotational kinetic energy: K = 1/2Iw2

The Attempt at a Solution



B1 = 1/2(32.2)(5)^2 = 402.5 ft-lb
B2 = 1/2((mr^2)/2)(5/2) = 201.25 ft-lb
B3 = 1/2(96.6)(5)^2 = 1207.5 ft-lb

My answers are way off, what am I doing wrong?
 
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How can energy be measured in ft-lb? That doesn't make sense unit wise.

A ft-lb is a unit of torque...
 
Matterwave said:
How can energy be measured in ft-lb? That doesn't make sense unit wise.

A ft-lb is a unit of torque...


Work = force * distance right?

force unit:lb
distance unit :ft
 
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