work energy theorm

Question 1

work

Answer 1

Work is said to be done, when a body a displaced through some distance in the direction
of applied force. The SI unit work is joule (J) and in CGS it is erg.
1 joule (J) = 10^(7)erg
W=Fs(cosθ)=Fs

Question 2

positive work

Answer 2

If value of the angle θ between the directions of F and s is either zero or
an acute angle

Question 3

negative work

Answer 3

If value of angle θ between the directions of F and s is either 180° or
an obtuse angle.

Question 4

zero work

Answer 4

● As work done W = ⋅ = F s F s cos , θ hence work done can be zero, if
(i) No force is being applied on the body, i.e. F = 0.
(ii) Although the force is being applied on a body but it is unable to cause any
displacement in the body, i.e. F ≠ 0 but s = 0.
(iii) Both F and s are finite but the angle θ between the directions of force and
displacement is 90°. In such a case
W = ⋅ F s = = ° = F s F s cos cos θ 90 0

Question 5

work done by variable force

Answer 5

W=∫F.ds

work done=area under the curve

Question 6

conservative forces

Answer 6

A force is said to be conservative if work done by or against
the force in moving a body depends only on the initial and
final positions of the body and not on the nature of path
followed between the initial and the final position.
Gravitational force, force of gravity, electrostatic force are
some examples of conservative forces (fields)

Question 7

non-conservative forces

Answer 7

A force is said to be non-conservative if work done by or
against the force in moving a body from one positions to
another, depends on the path followed between these two
positions. Force of friction and viscous force are the examples
of non-conservative forces.

Question 8

energy

Answer 8

Energy is defined as the capacity or ability of a body to do
work. Energy is scalar and its units and dimensions are the
same as that of work.

Question 9

kinetic force

Answer 9

K=1/2mv^2
kinetic energy as momentum
k=p^2/2m and p=√2mK

Question 10

Relation between kinetic energy and force i

Answer 10

KE/FORCE=v x t/2

Question 11

potential energy

Answer 11

Potential energy is the energy stored in a body or a system by
virtue of its position in a field of force or due to its
configuration. Potential energy is also called mutual energy or
energy of the configuration.