Dynamics - Conservation of Energy example 2

Thermodynamics: drive.google.com/file/d/1bFzQ...
Mechanics of Materials: drive.google.com/file/d/1P-pc...
Statics: drive.google.com/file/d/1aYY5...
Dynamics: drive.google.com/file/d/1_JTk...

[@abbastufan7508]

why dont we use the cosine component of the F on the block?

[@abbastufan7508]

sorry sin component

[@porterd3160]

Why don’t we use 2T here?

[@porterd3160]

Wrong problem

[@Johnngvyn]

When would you know when to use: sumU=delta T vs V+T+U=V+T

[@morolayomi]

I have come to the conclusion that it has to do with the presence of external force. When there is non conservative force, it is highly likely that we use the Work Energy Theorem. So look out for those

[@yigitcan824]

They are same actually ,You can use either of them