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Blocks connected by rope, Newton's Third Law 
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#1
Mar1408, 08:10 AM

P: 267

The figure shows two 1.0 kg blocks connected by a rope. A second rope hangs beneath the lower block. Both ropes have a mass of 250 g. The entire assembly is accelerated upward at by force. What is F? What is the tension at the top end of rope 1? What is the tension at the bottom end of rope 1? What is the tension at the top end of rope 2?
The force on block B: T(m of B)g=(m of B)a The force on block A: F[(m of a + m of b)g] = (m of b)a What do I do now? Thank you. Stephen 


#2
Mar1408, 08:20 AM

Mentor
P: 41,323

To find F, consider the masses and ropes as a single system. What external forces act on the system? What's the acceleration?



#3
Mar1408, 11:03 AM

P: 267

The figure shows two 1.0 kg blocks connected by a rope. A second rope hangs beneath the lower block. Both ropes have a mass of 250 g. The entire assembly is accelerated upward at by force. What is F? What is the tension at the top end of rope 1? What is the tension at the bottom end of rope 1? What is the tension at the top end of rope 2?
If we make it one system the external forces are: F and weight of the blocks So F= (m of a + m of b + 2*m of rope)a and w=(m of a + m of b + 2*m of rope)g since Fw=(m of a + m of b +2*m of rope)a, right?? Now what?? Thank you. 


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