# Work Energy Theorem

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According to this theorem, the work done by all the forces (conservative or non-conservative, external or internal) acting on a particle or an object is equal to the change in kinetic energy of it.

Let , ... be the individual forces acting on a particle. The resultant force is and the work done by the resultant force is:

where is the work done on the particle by and so on. Thus, work energy theorem can also be written as: **Work done by the resultant force is equal to the sum of the work done by the individual forces**. There are a few points worth noting:

- ) If
*W*_{net}is positive then*K*_{f}-*K*_{i}= +ve (positive),*i.e*,*K*_{f}>*K*_{i}or kinetic energy will increase and vice versa. - ) This theorem can be applied to non-inertial frames also. In a non-inertial fram it can be written as:
**Work done by all the forces (including pseudo forces) = change in kinetic energy in non-inertial frame.**