Question

Match the column A with column B

Column 1	Column 2
Work done by a weight lifter in bringing down a weight from a height	Work done is negative
Work done by the gravitational force on a freely falling body.	Work done is positive
A body moving on a rough surface	Mechanical energy is conserved
A ball moving on a smooth surface.	Mechanical energy is not conserved

Answer 1

Part A

1. When force and displacement are in opposite directions work is said to be negative.
2. Work done by a weight lifter in bringing down a weight from a height is negative

Hence, (A)-(I)

Part B

1. When force and displacement are in the same directions work is said to be positive.
2. Work done by gravity on a freely falling body is positive since displacement and force are in the same direction.

Hence, (B)-(II)

Part C

1. Frictional force is a non-conservative force since in frictional force work done depends upon the path taken by an object.
2. When a frictional force acts on a body, its mechanical energy is not conserved.

Hence, (C)-(IV)

Part D

1. Frictional force is a non-conservative force since in frictional force work done depends upon the path taken by an object.
2. When there is no frictional force acting on a body the mechanical energy is conserved.

Hence, (D)-(III)

Column A	Column B
A. Work done by a weight lifter in bringing down a weight from a height	I. Work done is negative
B. Work done by the gravitational force on a freely falling body.	II.Work done is positive.
C. A body moving on a rough surface	IV. Mechanical energy is not conserved
B.A ball moving on a smooth surface.	III.Mechanical energy is conserved