Question

a) if energy is not a vector, what is the diffwrneve between a "+" work and a "-" work?

b) Give an example of a system in which the total energy is constant, yet energy is transferred by work

c) An onjevg slides across a surface. there is friction betwren the objecy and the surface. explain why the work done by friction misg be included on the right side of the equations delta E = W even if borh the objecg and the surface are included in the system used to analyze the situation.

d) do you supoise that the force between two magnegs would be conservative? Explain your reasoning

Answer 1

a) We know that work done W=(Force. displacement), when the displacement is along the direction of force then the work done is said to be positive but if the displacement is opposite to the direcdire of force then the work done is negative.

b) We can consider a system of two particles of mass m1 and m2 respectively, moving towards each other and undergoing collision. In this case the total energy of the system will be conserved or constant but the particles displaces so the work is done.

c) When we analyze a system where a object moves across a frictional surface, then the displacement of the object is eventually affected by the friction due to the surface also. So, while considering the total change in energy (delta)E= W, the work done due to the friction also comes into action.

d) A force is said to be conservative if the work done by the object is independent of path taken. In case of the force between two magnetic poles, the forces are central forces that acts along the line joining the center of two magnets. So, here thhe central force is spherically symmetric, it is conservative force.