Work, Energy & Power
Work: Work done W is defined as the dot product of force F and displacement s.
Work = F.s = Fs cos θ
Here θ is the angle between Force and displacement.
Work done by a variable force:
If applied force F is not a constant force, then work done by this force in moving the body from
position A to B will be,
𝑏
𝑊= 𝐹 . 𝑑𝑠
𝑎
Here ds is the small displacement.
Units: The unit of work done in S.I is joule (J) and in C.G.S system is erg.
1J = 1 Nm | 1 erg = 1 dyn.cm
1J = 107 erg
Power:
The rate at which work is done is called power and is defined as,
P = W/t = F.s/v = F.v
Here s is the distance and v is the speed.
𝑑𝐸
Instantaneous power in terms of mechanical energy: 𝑃 = 𝑑𝑡
Units: The unit of power in S.I system is J/s (watt) and in C.G.S system is erg/s.
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Work: Work done W is defined as the dot product of force F and displacement s.
Work = F.s = Fs cos θ
Here θ is the angle between Force and displacement.
Work done by a variable force:
If applied force F is not a constant force, then work done by this force in moving the body from
position A to B will be,
𝑏
𝑊= 𝐹 . 𝑑𝑠
𝑎
Here ds is the small displacement.
Units: The unit of work done in S.I is joule (J) and in C.G.S system is erg.
1J = 1 Nm | 1 erg = 1 dyn.cm
1J = 107 erg
Power:
The rate at which work is done is called power and is defined as,
P = W/t = F.s/v = F.v
Here s is the distance and v is the speed.
𝑑𝐸
Instantaneous power in terms of mechanical energy: 𝑃 = 𝑑𝑡
Units: The unit of power in S.I system is J/s (watt) and in C.G.S system is erg/s.
19
downloaded from cyberworldforu.blogspot.com
