WORK: The product of force applied on object and it’s displacement is known as work.
To get work done the displacement is necessary. If there is no displacement then work done is zero (If displacement=0).
Units for Work: MKS – Joule 1Joule= 1Newton X 1metre.
CGS – Erg 1Erg= 1Dyne X 1 cm.
FPS – Foot Poundal 1foot poundal = 1foot X 1Poundal.
1Joule = 107Erg …. As 1Joule = 1N X 1m.
= 1000gm X 100cm X 100cm …..(1N=1Kg X 1m= 1000gm X 100cm).
= 107Erg.
Practical Units Of Work: Kg-m 1kg-m = 1kg X 1m. (1kg-m = 9.8 Joules)
gm-cm 1gm-cm = 1gm X 1cm.
foot-pound 1foot-pound = 1foot X 1pound.
ELECTRICAL WORK: Under 1 volt of potential when current flowing is 1ampere in any electrical circuit then work done is 1 watt.
1Watt = 1Volt X 1amp.
Energy = Power in watts X Time in seconds.
1Joule = 1 watt X 1 second.
PRCATICAL UNIT OF ELECTRICAL ENERGY: KWh.
1KWh = 1 KW X 1hour.
=1000 Watt hours = 1Unit.
WORK DONE IN DIFFERENT DIRECTION: A) When angle between direction of force and actual diplacement is given.
&the direction of force then,
work can be found as follows.
Work = Force X Displacement.
W = F X S COS
B) If the displacement is in circular motion.
If Force = F …working perpendicular to the radius of circle.
Radius = r.
Number of revolutions = n.
Work done = Force X Displacement in ‘n’ rpm.
= F X n X Circumference of Circle.
= F X n X 2πr
= Torque X Angle in Radian.
= F X r X 2πn
(Torque= Force X Radius )
POWER: Rate of doing work is called Power.
Power =
HORSE POWER: It’s the bigger unit to measure the industrial power.
1HP (Metric) = 75 kg-m/sec. (4500 kg-m/sec) = 735.5 Watt. 1KW =1.3596 HP(Metric). | 1HP (Britsh) = 550 ft-pound/sec. =746 Watt. 1KW =1.34HP(British). |
1Watt=1Jopule/sec |
