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Work, Energy and Power

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Physics Part I

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Physics

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CBSE Gujarat Board Haryana Board

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Class 10 Class 12

Two particles of masses m1,m2 move with initial velocities u1 and u2. On collision, one of the particles gets excited to a higher level, after absorbing energy (E). If final velocities of particles be v1 and v2, then we must have

  • straight m subscript 1 superscript 2 straight u subscript 1 space plus straight m subscript 2 superscript 2 straight u subscript 2 space minus straight epsilon space equals space straight m subscript 1 superscript 2 space straight v subscript 1 space plus straight m subscript 2 superscript 2 straight v subscript 2
  • 1 half m subscript 1 u subscript 1 superscript 2 space plus 1 half m subscript 2 u subscript 2 superscript 2 space equals space 1 half m subscript 1 v subscript 1 superscript 2 space plus 1 half m subscript 2 v subscript 2 superscript 2 minus epsilon
  • 1 half m subscript 1 u subscript 1 superscript 2 space plus 1 half m subscript 2 u subscript 2 superscript 2 space minus straight epsilon space equals space 1 half m subscript 1 v subscript 1 superscript 2 space plus 1 half m subscript 2 v subscript 2 superscript 2
  • 1 half m subscript 1 u subscript 1 superscript 2 space plus 1 half m subscript 2 u subscript 2 superscript 2 italic space italic plus epsilon space equals space 1 half m subscript italic 1 superscript italic 2 v subscript 1 superscript 2 space plus 1 half m subscript italic 2 superscript italic 2 v subscript 2 superscript 2

C.

1 half m subscript 1 u subscript 1 superscript 2 space plus 1 half m subscript 2 u subscript 2 superscript 2 space minus straight epsilon space equals space 1 half m subscript 1 v subscript 1 superscript 2 space plus 1 half m subscript 2 v subscript 2 superscript 2
Total space initial space energy space equals space 1 half straight m subscript 1 straight v subscript 1 superscript 2 space plus 1 half straight m subscript 2 straight v subscript 2 superscript 2
since space after space collision space one space particle space absorb space energy space straight epsilon space
therefore space Total space final space energy space equals space 1 half m subscript 1 v subscript 1 superscript 2 space plus 1 half m subscript 2 v subscript 2 superscript 2 italic space italic plus epsilon
F r o m italic space c o n s e r v a t i o n italic space o f italic space e n e r g y italic comma
rightwards double arrow space 1 half m subscript 1 u subscript 1 superscript 2 space plus 1 half m subscript 2 u subscript 2 superscript 2 space minus straight epsilon space equals space 1 half m subscript 1 v subscript 1 superscript 2 space plus 1 half m subscript 2 v subscript 2 superscript 2
Total space initial space energy space equals space 1 half straight m subscript 1 straight v subscript 1 superscript 2 space plus 1 half straight m subscript 2 straight v subscript 2 superscript 2
since space after space collision space one space particle space absorb space energy space straight epsilon space
therefore space Total space final space energy space equals space 1 half m subscript 1 v subscript 1 superscript 2 space plus 1 half m subscript 2 v subscript 2 superscript 2 italic space italic plus epsilon
F r o m italic space c o n s e r v a t i o n italic space o f italic space e n e r g y italic comma
rightwards double arrow space 1 half m subscript 1 u subscript 1 superscript 2 space plus 1 half m subscript 2 u subscript 2 superscript 2 space minus straight epsilon space equals space 1 half m subscript 1 v subscript 1 superscript 2 space plus 1 half m subscript 2 v subscript 2 superscript 2
2032 Views

Is work a scalar or a vector quantity?

Work is dot product of two vectors. i.e. F with rightwards arrow on top times S with rightwards arrow on top.

And dot product is a scalar quantity. Therefore, work is a scalar quantity. 
1450 Views

What is watt?

SI unit of power is Watt. 
773 Views

Define watt.

Power is said to be one watt if one joule of work is done in one second. 
860 Views

What are different units of energy?

The different units of energy are :

(i) Joule            
(ii) Erg
(iii) eV            
(iv) KWh
(v) Calorie.

804 Views

Define the unit joule.

Work done is said to be one joule if one newton of  force displaces the body through a distance of one meter in the direction of applied  force .
799 Views