Dynamcis 03_02 Force Mass and Acceleration Problem with Solution in Rectilinear Motion of Kinetics

The system is released from rest with the cable taut.
For the friction coefficients s= 0.25 and k= 0.20 ,
calculate the acceleration of each body and the tension T in the cable. Neglect the small mass and friction of the pulleys.

[@bikram2017]

At last I can say : thank you sir 🙏🙏🙏🙏🙏🙏🙏🙏

[@ForaKotola]

The mass of the block B is 20..but you just used 15 why?

[@pematsomu6146]

Sir How mass of B is 15 it should be 20 na sir

[@KasmaTutorial]

You are absolutely correct.
it is a writing and narration error. Don't worry, the calculations are done with 20 lb. It has no change in results. Thank you for your valuable comment.

[@asfandyarkhan5037]

yes i was also confused

[@Johnngvyn]

did you just assume a=2b?

[@KasmaTutorial]

Hi,
No, it is not assumptions. It is the constraints motion.
A is suspended with a single rope while B is suspended with a doubled rope. That is why A = 2B, i.e., if A moves 1 m, B will move a half meter.

[@KHATTAB777]

Why
Sa-2Sb =0
And not Sa+2Sb=0

[@KasmaTutorial]

The main thing is Sa is twice of Sb. In addition to this, the plus and the minus sign will be used based on the positive axis reference for each particle.
Assume Particle A moves in the upward and particle B in the downward direction.
For particle A, if you assign positive to the upward (+ve Sa) and for particle B, in the downward direction(+ve 2Sb), you can use
Sa +2Sb = 0.
However, if you assign positive in the upward for particle B, you can use
Sa - 2Sb = 0.
Thanks for your amazing question.

[@sebastiangomez8199]

does anybody know from what text book was this problem taken out of?

[@oseamiya3663]

Haha, Mass is 20 but everytime he writes 15

[@KasmaTutorial]

You are correct.
it is a writing and narration error. Don't worry, the calculations are done with 20 lb. It has no change in results.
Thank you for your valuable comment.

[@ForaKotola]

​@@KasmaTutorial.tnx teacher.i was confused ,,