Test: Conservative Forces - JEE MCQ

When the man pulls the bucket outside the well the gravitational potential of the man + bucket system increases and hence the work done by the gravitational force is negative.

Potential energy at a point is defined in terms the amount of work done, which is defined in terms of force and thus we get potential as an integral of force applied over some position x. Hence F(x) = -dU(x) / dx which is the differentiation of potential energy wrt position.

The friction is the phenomena that defines that there is a resistance which is present there between the two surfaces. This friction is applied tangentially to the surfaces in contact. Thus the main thing is that the forces on both of the surfaces act tangential to each other.

A conservative force is a force with the property that the total work done in moving a particle between two points is independent of the taken path. Equivalently, if a particle travels in a closed loop, the total work done (the sum of the force acting along the path multiplied by the displacement) by a conservative force is zero.

Frictional force, Air-resistance, viscous force all these forces work against each other i.e., they are opposing forces, while electrostatic force is not a opposing force.

A force is said to be conservative if the work done by or against the force on a body is independent of path followed by the body and depends only on initial and final positions.
Work done by or against the conservative force in moving a particle along a closed path is zero.
Hence C is correct.

In an inelastic collision, the force of reformation is not equal to the force of deformation and thus some amount of energy is lost. But still as no external force acts upon the system momentum is still conserved.

We have a relation between potential energy and work done:
The negative sign just shows the inverse relation between potential energy and work done by conservative force.

A force is said to be conservative if the work done by or against the force on a body is independent of path followed by the body and depends only on initial and final positions.
Work done by or against the conservative force in moving a particle along a closed path is zero.