- #1
wcase
- 9
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The problem is:
In the figure here three ballot boxes are connected by cords, one of which wraps over a pulley having negligible friction on its axle and negligible mass. The masses are mA = 31 kg, mB = 40 kg, and mC = 13 kg. When the assembly is released from rest, (a) what is the tension in the cord connecting B and C, and (b) how far does A move in the first 0.250 s (assuming it does not reach the pulley)?
Where block A is sitting on a table connected to a string that goes to a pulley at the end of the table where bock B and C are hanging.I've read this question all over the internet and cannot interpret the results, I see what's being done, but I don't understand.
For the string between A and B, the tension is said to be mA*a, but why is there no influence from block B on the tension of the first string? shouldn't the tension be (mB+mC)*g since there would be no tension if the two blocks are pulling it down?
For block B, the net Force Fb=mB*a so 40a = Fb, and since the tension on the string between A and B is pulling it up and the tension on the string between B and C is pulling it down, 40a=40g-T1+T2.
For block C Fc=13a=13g+T2
so T2=13a-13g
and T2=40a-40g+T1
And that is where I am stuck, I do not know how to get T1
In the figure here three ballot boxes are connected by cords, one of which wraps over a pulley having negligible friction on its axle and negligible mass. The masses are mA = 31 kg, mB = 40 kg, and mC = 13 kg. When the assembly is released from rest, (a) what is the tension in the cord connecting B and C, and (b) how far does A move in the first 0.250 s (assuming it does not reach the pulley)?
Where block A is sitting on a table connected to a string that goes to a pulley at the end of the table where bock B and C are hanging.I've read this question all over the internet and cannot interpret the results, I see what's being done, but I don't understand.
For the string between A and B, the tension is said to be mA*a, but why is there no influence from block B on the tension of the first string? shouldn't the tension be (mB+mC)*g since there would be no tension if the two blocks are pulling it down?
For block B, the net Force Fb=mB*a so 40a = Fb, and since the tension on the string between A and B is pulling it up and the tension on the string between B and C is pulling it down, 40a=40g-T1+T2.
For block C Fc=13a=13g+T2
so T2=13a-13g
and T2=40a-40g+T1
And that is where I am stuck, I do not know how to get T1