Classes by Mahendra Rajak

1. WORK,POWER
&
ENERGY
MAHENDRA RAJAK
(TGT P&HE) KVS MAHABUBNAGAR
1ST RANK (CGPSC SPORTS OFFICER)
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2. 2

3. WORK
Work – In Bio-Mechanics the term work has a much more limiting meaning.
“Whenever a force acts on a body, the work done by the force is equal to
the product of its magnitude and the distance that the body moves in the
direction of the force, while the force is being applied to it”.
"जब भी कोई बल ककसी प िंड र कार्य करता है, तो बल द्वारा ककर्ा गर्ा कार्य उसक
े
ररमाण क
े गुणनफल क
े बराबर होता है और वह प िंड बल की दिशा में गतत करता है,
जबकक उस र बल लगार्ा जा रहा है"
Expressed in algebraic form :-
W = Fd
W = The work done by the force
F = Magnitude of the force
d = The appropriate distance
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4. +ve Work
If the body moves in the direction of force application.
Ex. :- Lifter, Bench press exit constant upward force and make the bar ball
to a distance.0.5m upward direction he does the work(1800 N x o.5m) 900
N.M the work is said to be positive because the direction in which the body
moves, is the same as that in which the force acts. If the force acts in the
opposite direction in which the body moves, Negative work is said to done
by the force. Thus in the example the wt lifter work done by the upward
force is positive and the work done by gravity (wt of the bar ball say 1400
N) is negative,that is:
W = - (1400 X 0.5)
W = - 700 N.M
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5. Ex. Lifter applied force upward direction and make the bar ball to move
the distance of 1mt.
Total work done
(900-700) 200 NM
Unit of work are unit of force multiplied by unit of distance . In the
metric system the common unit of force is (N) multiplied by a common
unit of distance (M)
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6. -ve work
bring wt done – work done. –ve because force is opposite to direction of force if the wt
of bar ball is 70 kg.
W=70 x 1mt
W= 70 kg m
3) Total work done = 80 – 70 = 10 kg m
4) Useful work Total work done wtx d
useful work done wt x h
W x d 4 mt 2mt
80 x 4
80kg x 4m = 320 kg. m
80kg x 2m = 160 kg m
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7. POWER
The term power brings in the use of time factor with regard to
work done as is define : “The rate at which the work is perform,
for arrive at
P = W
t
this value the work done is divided by the time taken.
When P = the power developed = w= work done, t = time taken.
P = Work done
Time taken
Shorter the time taken to work done, quicker the person, where
work is same.
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8. P = W or P = F x d –
t t
P = F x d –
t
Where d/t = distance covered per unit time
P=F x V – (V=average velocity)
Or
In other words – The event which have structure in quickness
movement – They are power based & vice versa --- ex--- sprit, throw,
jump are power event – larger distance races are endurance oriented
-“The capacity to do work”.
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9. ENERGY
• The term energy represented the potentiality to do
work and this potentiality is mechanical developed
either
• by virtue of the height energy on which the object is
held or placed.
• by virtue deformation in shape or by virtue of
movement (motion) which the object perform.
There are two forms of mechanical energy.
Two types : 1- Kinetic energy 2- Potential energy
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10. 1- Kinetic energy -
The energy that a body possesses because it is in
motion is called kinetic energy.
The energy that a body possesses as a result of its
linear motion is given by equation.
KE=½ mv2 = 100 kg. – run by 9 m/sec
KE=½ (100 x 92 =)4050 kg (m/s) 2
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11. 2- Potential energy -
The energy that a body possesses because it is some
distance above the level of earth surface and can do
work in returning to that level is called its potential
energy.
PE = Wh
W = weight of body
H = height of body above the earth
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12. Law Conservation of Energy
With regards to different forms of energy the law of
conservation of energy
“state that “Energy can neither be created nor
destroyed but it can be changed from one form to
another”.
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13. Thanku
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