31.7 Worked Example - Two Blocks and a Pulley Using Energy

[@BoZhaoengineering]

your intepretation is very clear especially the energy change is zero and the potential energy change is negative work due to dot product. I love this math expression on this situation. Recall that I never got it done right in my high school.

[@HowViolet]

The greatest miracle here is how he’s writing backwards

[@drjimbo1357]

inverted video perchance?

[@cafe-tomate]

Why not taking into account the work of the internal force of the friction rope-pulley ? The work-KE theorem you derived in previous video accounts for work of internal + external forces (since F=ma has to be integrated for each individual particle of the system) You should have adopted the same method as in the next video (applying Newton's second law and torque law). Otherwise, using W-KE theorem leads to a rope-pulley friction term. That means this method is suited in case we want to calculate the rope-pulley friction term.

[@liuhh02]

Awesome! Thank you very much for your clear explanation.

[@PremiDhruv]

if friction is zero, why will the pulley rotate ?

[@cafe-tomate]

Frictionless assumption is only taken for mass 1

[@somerandomgtryingtomakeit]

❤

[@nacicelik1954]

Hf must be on the ground or not?

[@mehdiezzine292]

no , you choose where you put your 0 value for problems like that , you just have to be consistent with it