How to solve Work And Energy/kinetic energy problems

Work and energy /kinetic energy problems are quite challenging questions. We need to clear concept and direction to solve them correctly. Here is How to solve Work And Energy problems
Choose your frame of reference. Kinetic Energy will differ in each reference frame while Potential energy will remains constant
Define your system, which may include two or more interacting particles, as well as springs or other systems in which elastic potential energy can be stored. Choose the initial and final points.
Identify zero points for potential energy (both gravitational and spring). If there is more than one conservative force, write an expression for the potential energy associated with each force.
Determine whether any non conservative forces are present. Remember that if friction or air resistance is present, mechanical energy is not conserved.
Determine whether any external forces are present. Remember that external forces are present, mechanical energy is not conserved.
If mechanical energy conserved, you can write the total initial energy at some point

$E_i=PE_i+KE_i$

Then, write an expression for the total final energy at the final point that is of interest

$E_f=PE_f+KE_f$

Because mechanical energy is conserved, you can equate the two total energies and solve for the quantity that is unknown.

$E_i= E_f$
$PE_i+KE_i=PE_f+KE_f$

If frictional forces are present (and thus mechanical energy is not conserved), first write expressions for the total initial and total final energies. In this case, the difference between the total final mechanical energy and the total initial mechanical energy equals the change in mechanical energy in the system
due to friction.
If external forces are present (and thus mechanical energy is not conserved), first write expressions for the total initial and total final energies. In this case, the difference between the total final mechanical energy and the total initial mechanical energy equals the change in mechanical energy in the system
due to external force.
If both external forces and frictional forces are present (and thus mechanical energy is not conserved), first write expressions for the total initial and total final energies. In this case, the difference between the total final mechanical energy and the total initial mechanical energy equals the change in mechanical energy in the system due to external force and friction

This is well explained with example in the below video also

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