The discussion centers on the relativity of force and work in different reference frames, particularly using the example of a book on a table and a moving train. When a force is applied to the book, the work done can be positive or negative depending on the frame of reference considered, such as the ground or the train. The frictional force also plays a crucial role, exhibiting both positive and negative work depending on the context. Ultimately, while energy and work are frame-relative, the magnitude of force remains invariant across inertial frames in classical physics.
PREREQUISITESPhysics students, educators, and anyone interested in understanding the principles of force, work, and energy in various reference frames.
The direction we push and the direction the book moves need not be the same. Consider a book on a train. We push the book rearward relative to the moving train. The book moves forward relative to the ground and the work we perform relative to the ground frame is negative.manogyana25 said:When a book which is on table is pushed, it moves in the direction we push and the work done by us is positive and the energy gained by the body is also positive.
The force of friction on that book is in the forward direction. The book is moving in the forward direction relative to the ground. Relative to the ground, the work done by friction was positive.But consider the frictional force. The work done by it is negative.