Question

Which of the following statements is/are correct about work? (The question has multiple correct options)
A. In a certain reference frame, ${W_{pseudo\;force}} + {W_{conservattive\;force}} + {W_{non - conservattive\;force}} + {W_{other\;forces}} = \Delta K$
B. Work done by friction is always negative.
C. Work done by a force is defined as the dot product of the force and the displacement of the point of application of force.
D. Work done by conservative force in moving a body from A to B = potential energy of the body at A – potential energy of the body at B.

Answer 1

The function performed by each and every force is equal to the change in kinetic energy, $\Delta K$ according to the working energy theorem. In vector form, ${\text{work}} = \overrightarrow F \bullet \overrightarrow S$. Only conservative forces will shift potential energy.

Complete step by step answer:
${W_{pseudo\;force}} + {W_{conservattive\;force}} + {W_{non - conservattive\;force}} + {W_{other\;forces}} = \Delta K$.
The given expression is correct according to the theorem of work energy. It implies that the sum of work done by pseudo force, conservative force, non-conservative force, and other forces is equal to the change in kinetic energy, $\Delta K$.

In nature, positive, negative or zero work done can be achieved by friction. Kinetic energy will decrease as the frictional force is opposed to velocity.

In physics, work is the method of moving energy to an object's motion by the application of a force which is often described as the result of force and displacement. If the force $F$ is constant and the angle in between force and the displacement $s$ is $\theta$, therefore the work performed is accomplished by $W = Fs\cos \theta$.

A conservative force occurs where the work performed on an object by that force is independent of the direction of the object. The function undertaken by a conservative force, therefore, depends only on the end points of the wave. Gravity is one example of a conservative force.

So, the correct answers are “Option A,C and D”.

Note:
Note that in this question it is mentioned that there may be more than one correct option. The options are related to the work done, so check each and every option according to the theorem of work energy.
Sum of all the forces is equivalent to the change in kinetic energy.
Work done obtained by the friction is not only negative but also positive and zero. Hence, option B is not a correct one.