Work done by the force is equal to the product of the Force and Displacement of the object in the direction of Force.
Work is a Scalar Quantity. Its SI Unit is Joule and CGS Unit is erg.
∴ 1 joule = 107 erg
Its dimensional formula is [ML2T-2].
Work done by a force is zero, if
(a) body is not displaced actually, i.e., s = 0
(b) body is displaced perpendicular to the direction of force, i.e.,
θ = 90°
- Work done by a force is positive if angle between F and s is acute angle.
- Work done by a force is negative if angle between F and s is obtuse angle.
- Work done by a constant force depends only on the initial and final Positions and not on the actual path followed between initial and final positions.
Work done in different conditions
(i) Work done by a variable force is given by
W = ∫ F * ds
It is equal to the area under the force-displacement graph along with proper sign.
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POWER
The rate of work done by a body is called its power.
Power = Rate of doing work = Work done / Time taken
If under a constant force F a body is displaced through a distance in time t, then power=
P= W / t = F × s / t
∴ P = F * v = F v cos θ
where θ is the smaller angle between F and v.
Power is a scalar quantity. Its S1 unit is watt and its dimensional formula is [ML2T-3].
Its other units are kilowatt and horse power,
1 kilowatt = 1000 watt
1 horse power = 746 watt
Energy
Energy of a body is its capacity of doing work.
It is a scalar quantity.
Its S1 unit is joule and CGS unit is erg. Its dimensional formula is [ML3T-3].
There are several types of energies, such as mechanical energy (kinetic energy and potential energy), chemical energy, light energy, heat energy, sound energy, nuclear energy, electric energy etc.