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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

A force straight F with rightwards arrow on top space equals space left parenthesis 5 straight i with hat on top space plus 3 straight j with hat on top space plus 2 straight k with hat on top right parenthesis space straight N is applied over a particle which displaces it from its origin to the straight r with rightwards arrow on top space equals space left parenthesis 2 straight i with hat on top minus straight j with hat on top right parenthesis space straight m.The work done on the particle in joules is

  • -7

  • +7

  • +10

  • +13


B.

+7

Work done in displacing the particle
straight W space equals space straight F with rightwards arrow on top space. straight r with rightwards arrow on top
space equals space left parenthesis 5 straight i with hat on top space plus space 3 straight j with hat on top space plus 2 straight k with hat on top right parenthesis. left parenthesis 2 straight i with hat on top space minus straight j with hat on top right parenthesis
space equals space 5 space straight x space 2 space plus 3 space straight x space left parenthesis negative 1 right parenthesis space plus space 2 straight x 0
space equals space 10 minus 3
equals space 7 straight J

Work done in displacing the particle
straight W space equals space straight F with rightwards arrow on top space. straight r with rightwards arrow on top
space equals space left parenthesis 5 straight i with hat on top space plus space 3 straight j with hat on top space plus 2 straight k with hat on top right parenthesis. left parenthesis 2 straight i with hat on top space minus straight j with hat on top right parenthesis
space equals space 5 space straight x space 2 space plus 3 space straight x space left parenthesis negative 1 right parenthesis space plus space 2 straight x 0
space equals space 10 minus 3
equals space 7 straight J

209 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 are different units of energy?

The different units of energy are :

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

804 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

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