# Doubt: Basic question on Work-Energy Method?

• dexter1
In summary, the work-energy method can be applied for a body sliding down an inclined plane or vertically falling, and you should only consider the change in kinetic energy when solving the problem. This is because the work done by all forces, including gravity, will equal the change in kinetic energy.

#### dexter1

I have a basic doubt on application of work energy method,

1. Can I apply work-energy method (i.e. work done equals to change in kinetic energy(KE)) for a body sliding down the inclined plane? If yes, while solving the problem i should use only change in KE or sum of change in KE & PE(potential energy), as heigh of the body is changing while sliding down? I am pretty confused kindly explain in detail..

2. What if in case of a a body vertically moving down/falling? In this case, it should be KE only or PE only or Sum of KE&PE? and Why?

I referred some books and while solving any of the above problems, they used work done = change in kinetic energy, i am confused why they are not considering PE in these situations?

dexter1 said:
I have a basic doubt on application of work energy method,

1. Can I apply work-energy method (i.e. work done equals to change in kinetic energy(KE)) for a body sliding down the inclined plane? If yes, while solving the problem i should use only change in KE or sum of change in KE & PE(potential energy), as heigh of the body is changing while sliding down? I am pretty confused kindly explain in detail..
Yes you can apply it. See my comment below.

2. What if in case of a a body vertically moving down/falling? In this case, it should be KE only or PE only or Sum of KE&PE? and Why?
Again, see my comment below.

I referred some books and while solving any of the above problems, they used work done = change in kinetic energy, i am confused why they are not considering PE in these situations?
The work-energy theorem says that if you consider the work done by all forces (including gravity) it will equal the change in the kinetic energy (not total energy). And that's just what happens.

If you consider the work done by all forces except gravity, then the work done will equal ΔK + ΔU. (The work done by gravity is already included in the potential energy term.)

## 1. What is the Work-Energy Method?

The Work-Energy Method is a physics concept that relates the work done on an object to the change in its kinetic and potential energy. It states that the net work done on an object is equal to the change in its kinetic energy, which can also be expressed as the sum of its initial and final potential energies.

## 2. How is the Work-Energy Method used in analyzing motion?

The Work-Energy Method is used to analyze motion by considering the forces acting on an object and the work done by those forces to determine the change in the object's kinetic energy. This method is particularly useful for systems with non-conservative forces, such as friction, where the work done by these forces must also be considered.

## 3. What are the limitations of the Work-Energy Method?

The Work-Energy Method is limited in that it can only be used to analyze motion in a straight line and cannot account for rotational motion. It also assumes that the net work done on an object is equal to the change in its kinetic energy, which may not always be the case in complex systems.

## 4. How does the Work-Energy Method relate to the Law of Conservation of Energy?

The Work-Energy Method is based on the Law of Conservation of Energy, which states that energy cannot be created or destroyed, only transferred or converted from one form to another. In the case of the Work-Energy Method, the work done on an object is converted into changes in its kinetic and potential energies, while the total energy of the system remains constant.

## 5. Can the Work-Energy Method be applied to all types of systems?

The Work-Energy Method can be applied to most systems, as long as the forces acting on the object and the change in its kinetic energy can be accurately measured. However, it may not be applicable in cases where the system is highly complex or involves non-conservative forces that cannot be easily quantified.